Now that swscale can handle RGB chroma's, let's try to use is where we can, it is likely a lot faster.

As live555 provides only static lib and we build a plugin, we need to use p$
This partially revert [7b0dd84f]

I have tested that RGBA blending to I420/YUY2/RV32/RV16 have the right colors.

Fix var_CreateGetBool/Integer mix up.
Fix an in valid free.
Fix an out of bound read.
Fix uninitialized variables.
(It may help with #1879)

i_rate can go up to 2^32-1.
If you * 1.044 it is going to not fit in a int (_framelength)

There is no point in loading the RTP access_demux if the MRL scheme
is not explicitly supported - it would fail in Open anyway.

mjpeg demux: When looking trough the data for EOI, also check for SOIs and skip the next EOI if we do find a SOI. This is to handle JPEG images which have JPEG thumbnails in their EXIF data.

core chroma: fix [6702c304] Restore YUV422 and YUV420 type formats to original values.

core chroma: Add support for YUV440 and YUVJ440. These are a rotated version of YUV422 and used with rotated JPEGs mostly.

ffmpeg chroma: This follows up on [0034fbab] by providing defaults in case no mask values were set.