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

[MyLive](https://mylive.in.th) is a streaming platform in Thailand.
Website founded in 2013 and company established in 2017.

Closes jp9000/obs-studio#1073

Closes jp9000/obs-studio#1079

Closes jp9000/obs-studio#1063

UI: Allow keyboard events on X11 fullscreen projector

It looks like the link between the gs layer rgba enable flags and the
underlying D3D states never got fully implemented.

This change adds the missing piece, fixing an issue I had in a plugin
wherein I couldn't write a blended value to a RGBA render target without
also changing the alpha of the dest pixel.  Debugging that led to the
missing gs_enable_color functionality.

Closes jp9000/obs-studio#1064

rtmp-services: Add us-west1 Picarto ingress

rtmp-services: Add Eventials streaming platform

This adds the ability for users to change the names of audio sources
from the mixer including desktop and mic/aux sources.

Closes jp9000/obs-studio#1055

When device timing is used, it shouldn't be modifying the timestamp.
Fixes an issue where certain devices with large audio segments would
seem a bit out of sync.

UI: Add Frontend API function to save replay buffer

UI: Disable source copy if no sources are selected

In the FFmpeg output, it was not passing the muxer settings to the
AVIOContext, so some settings would not be properly passed to protocols.

Closes jp9000/obs-studio#1035

This makes it so the buttons appear "pressed" while streaming/recording
to more visibly help indicate that they are currently active.

Closes jp9000/obs-studio#1039

linux-alsa: Display the "Custom" entry once only

The OBSBasicFilters window did not register a handler for the
"update_properties" signal. Now it does. Addresses issue #1028.

Closes jp9000/obs-studio#1036

(This commit also modifies the deps/media-playback, obs-ffmpeg, and
win-dshow modules)

More fixes due to ffmpeg renaming some constants and deprecating
AVFMT_RAWPICTURE and AV_PIX_FMT_VDA_VLD.
Latter replaced by AV_PIX_FMT_VIDEOTOOLBOX per ffmpeg dev advice.

Closes jp9000/obs-studio#1061

Prevents an issue where the output duplicator would cause the program to
crash if the graphics driver crashes and the graphics subsystem needs to
be rebuilt.

Closes jp9000/obs-studio#1076

This fixes that in studio mode disabled filters are applied to sources in
the live scene.

X11BypassWindowManagerHint  Bypass the window
           manager completely. This results in a borderless window
           that is not managed at all (i.e., no keyboard input unless
you call QWidget::activateWindow() manually).

This allows the Esc key to close the projector on X11

The default value in the .ui file was out of sync so the signal to
update the stacked widget was never sent.

Fixes https://obsproject.com/mantis/view.php?id=1060