Due to the recent change of using FFmpeg to decode MJPEG, MJPEG was
getting included in the delayed device check.  This fixes that so that
it doesn't.  MJPEG can decode in real time.

IsEncoded is meant to be used to indicated delayed devices, such as
older Elgato devices, or Hauppauge device.  Devices that use H264 and
have a 800+ millisecond latency.  This changes the function name to
better indicate that.

Fixes FFmpeg 4.0 deprecation warnings.

Fixes hardware decoding support and updates it to FFmpeg 4.0.

Optimize bicubic shader

(This also modifies the UI module)

Adds the ability for a source to monitor by default.  This is mainly
aimed at browser sources, so that they do not stop outputting audio by
default like they used to.

Add planar 4:2:2 video support; Use FFmpeg MJPEG decoder instead of DirectShow

Use bilinear filtering to reduce 16 taps to 9 for the regular path. This
works because the middle weights are always between 0 and 1, allowing
texture coordinates to be placed strategically to sample correct ratios.
I'm not sure about the undistort path, so I've left that alone.

Also remove weight normalization. I'm not seeing that make even a small
difference.

Intel HD Graphics 530, D3D11
644x478 -> 1323x1080: 1790 us -> 1279 us
1920x1080 -> 1280x720: 1301 us -> 918 us

References:
https://entropymine.com/imageworsener/bicubic/
http://vec3.ca/bicubic-filtering-in-fewer-taps/
http://developer.download.nvidia.com/books/HTML/gpugems/gpugems_ch24.html

When mixing sampling with raw loads in a shader, ending a shader with a
load would case the default sampler to become unset for OpenGL. Instead,
initialize with no sampler, and only set if there is a sampler.

UI: Add option to warn on stop recording

Measured lower CPU usage and latency than default DirectShow filter.
Tested with Logitech BRIO camera at 4K, 30 FPS.

This format has been seen when using FFmpeg MJPEG decompression.

GL support improvements

libobs: Rework RGB to YUV conversion

I think this was leftover from an abandoned approach.

UI: Improve look of adv audio control dialog

cmake: Install 'libobs.pc' under the correct 'libdir'

UI: Add Restream integration: stream info widget, channels widget

RGB to YUV converison was previously baked into every scale shader, but
this work has been moved to the YUV packing shaders. The scale shaders
now write RGBA instead. In the case where base and output resolutions
are identical, the render texture is forwarded directly to the YUV pack
step, skipping an entire fullscreen pass.

Intel GPA, SetStablePowerState, Intel HD Graphics 530, NV12

1920x1080, Before:
RGBA -> UYVX: ~321 us
UYVX -> Y: ~480 us
UYVX -> UV: ~127 us

1920x1080, After:
[forward render texture]
RGBA -> Y: ~487 us
RGBA -> UV: ~131 us

1920x1080 -> 1280x720, Before:
RGBA -> UYVX: ~268 us
UYVX -> Y: ~209 us
UYVX -> UV: ~57 us

1920x1080 -> 1280x720, After:
RGBA -> RGBA (rescale): ~268 us
RGBA -> Y: ~210 us
RGBA -> UV: ~58 us

This code path does not appear to be used. Breakpoint-inspected all four
output formats I420/I444/NV12/RGB, and they are all behaving as they
should.

OBS has an option to warn before stopping a stream, but it doesn't have
a similar warning for recording. This can result in a recording being
unintentionally stopped.

Add an option to warn when the "Stop Recording" button is pressed.

Note: While OBS also has an option to warn on stream start, this
patch purposefully does not add similar warn on recording start option.
This is because accidentally starting to record isn't risky in the same
way that accidentally starting to stream is.

frontend-tools: Add option to pause output timer when rec is paused

UI: Simplify resize output code

rtmp-services: Add Stripchat streaming service

UI: Declare missing overrides

Allows the users to find their stream key via a specified link if they
opt to just use a stream key instead of integration.

Allows testing bandwidth via streaming without the stream activating
remotely for viewers.

UI, obs-plugins: Add spinbox suffixes where necessary

cmake: Fix typo

libobs: Improve timing of unbuffered deinterlacing