CI: Fix curl download if file doesn't exist

rtmp-services: Add Mobcrush to services list

Fixes an issue where media-playback would not compile with older FFmpeg
versions due to the fact that the AV_PIX_FMT_VIDEOTOOLBOX was
unavailable until version 54.31.100 of libavutil (FFmpeg 2.8).

Fixes mantis issue 1045.

Closes jp9000/obs-studio#1089

Certain NVIDIA GPUs don't support NVENC, but ship with the NVENC
library, causing OBS to mistakenly think that NVENC is available when it
actually isn't.

Closes jp9000/obs-studio#1087

This commit adds Mobcrush RTMP ingest to services.json.

CI: Fix macOS builds on Travis CI's Xcode 8.3 image

The Travis CI Xcode 8.3 image uses macOS 10.12, where some OS and Xcode
components were changed. This commit should hopefully fix macOS
deployments on Travis for Xcode 8.3.

Jim note:

- Refactored code significantly
- Added a context menu option to exclude specific scenes from projectors
- Made it so multiview projectors update when scenes are
  added/removed/renamed
- Increased text quality
- Removed the color sources and replaced them with simple solid
  rectangles
- Increased the border size of "program" and "preview" scenes in the
  lower scene list

Closes jp9000/obs-studio#1068

Convenience function for setting a color (in hex format, e.g.
0xAARRGGBB)

CI: Fix Mac builds on Travis CI's Xcode 8.3 image

This reverts commit ca835ddf.

The Travis CI Xcode 8.3 image uses macOS 10.12, where some changes were
made to productsign, and Apple's documentation didn't clearly reflect
this. This commit should fix Mac builds on Travis for Xcode 8.3 and
clean up the job log.

CI: OSX - Use Xcode7.3

Travis changed the default OS X build environment from Xcode7.3 to
Xcode8.3 and it seems to have broken the packaging step somehow.
Fixes the issue by reverting to Xcode7.3.

The scene override would trigger, but the scene override variable would
stay set, causing the next transition to be the same one that was
previously used for overriding.

Fixes an issue where quick transitions would not function if the scene
has a transition override set for it.

If a preview projector was created in normal mode, it would become a
studio projector in studio mode.  The window title of the window
projector would reflect that it was in fact a preview projector and not
a program projector.

Allows the ability to override what specific transition a scene may use
when transitioning to it.

(Original proposal by cg2121, reworked by Jim)

Closes jp9000/obs-studio#1052

Ensures that private settings data is also duplicated when a scene or a
source is duplicated.

The studio mode program view projectors used the wrong saving mechanism.
The save data was copied from the source projectors, which were
dependent on string values, where as it should have been using a boolean
true/false value for specific monitors.

Implement automatic audio device selection for devices that use two
separate DirectShow filters for audio and video instead of having a
single filter with audio and video output pins.

Please note that this fix is currently only active for Elgato USB and
PCIe devices (e.g. Cam Link, HD60 S, HD60 Pro, 4K60 Pro) to avoid
unintentionally changing the behavior for any other devices (e.g.
webcams).

(Jim edit: This fixes an issue with newer Elgato devices where the
devices would not automatically have their audio coupled with the video;
users would have to manually select the audio device in order to get
audio functioning.)

Closes jp9000/obs-studio#1081

This commit adds a checkbox to general setting to allow users to enable
a vertically oriented layout for studio mode.

This commit addresses mantis issue 827:
https://obsproject.com/mantis/view.php?id=827

Closes jp9000/obs-studio#1072

Fixes a bug where the OBSBasic::programScene variable would not be set
for the new program scene when switching scenes via double-clicking on
them.

libobs: Fix height return value condition

This should fix "Output fails" when Rescale Output height set to 0.

(Note: This commit also modifies libobs-d3d11 and libobs-opengl)

Allows the ability to flush data directly without having to use the
buffer's internal data.

Allows the caller to manage his/her own vertex/index buffer data if
desired, working around the design flaw of having to rely on a
vertex/index buffer's internal data.

Prevents from having to pass ownership of buffer data from caller when
using gs_vertexbuffer_create() or gs_indexbuffer_create() (which is a
design flaw).

This commit allows a user to create projectors for the preview scene
instead of the program/live scene.

Close jp9000/obs-studio#1071

This adds the ability to switch to a scene by double-clicking it when in
studio mode.

(Edit by Jim: In case this change is undesired by the user, this has
been changed to be an option in general settings; disabled by default)

Closes jp9000/obs-studio#1029

Closes jp9000/obs-studio#983

Closes jp9000/obs-studio#983

Closes jp9000/obs-studio#983

(This commit also modifies the following modules: UI,
deps/media-playback, coreaudio-encoder, decklink, linux-alsa,
linux-pulseaudio, mac-capture, obs-ffmpeg, obs-filters, obs-libfdk,
obs-outputs, win-dshow, and win-wasapi)

Adds surround sound audio support to the core, core plugins, and user
interface.

Compatible streaming services: Twitch, FB 360 live
Compatible protocols: rtmp / mpeg-ts tcp udp
Compatible file formats: mkv mp4 ts  (others untested)
Compatible codecs: ffmpeg aac, fdk_aac, CoreAudio aac,
		   opus, vorbis, pcm (others untested).
Tested streaming servers: wowza, nginx
	 HLS, mpeg-dash : surround passthrough
Html5 players tested with live surround:
	 videojs, mediaelement, viblast (hls+dash), hls.js
Decklink: on win32, swap channels order for 5.1 7.1
         (due to different channel mapping on wav, mpeg, ffmpeg)
Audio filters: surround working.
Monitoring: surround working (win macOs linux (pulse-audio)).
VST:	 stereo plugins keep in general only the first two channels.
	 surround plugins should work (e.g. mcfx does).
OS: win, macOs, linux (alsa, pulse-audio).
Misc: larger audio bitrates unlocked to accommodate more channels
NB: mf-aac only supports mono and stereo + 5.1 on win 10
         (not implemented due to lack of usefulness)

Closes jp9000/obs-studio#968

Closes jp9000/obs-studio#1070

libobs: Copy enabled state when duplicating filters