Support streaming with zms (using ffmpeg) better
    * ZoneMinder compiles with ffmpeg 0.5..master
    * Make VideoStream class able to stream through ffmpeg better.
    * Ability to use fixed quality instead of fixed bitrate (by specifying bitrate 0...100)
    * Format url parameter supports <format>/<encoder> syntax

Details:
    - Redefine av_err2str to a to avoid compiler warning on newer g++'s
    - When using rtp format; if ffmpeg does not have a default codec, use CODEC_ID_MPEG4. (because this is what the default is as of 2.2 when this code was written)
    - Specify ofc->packet_size if rtp format is requested
    - Video generated in a thread to guarantee a constant fps.
    - Move _AVCODECID definition into zm_ffmpeg.h (and use instead of (AV)CodecID
    - Call avformat_network_init because ffmpeg warns about it beeing required soon.
    - increase VideoStream::video_outbuf_size to 4MiB to be able to encode larger pictures
A variable was referenced as a pointer when it was not.
- Removed an unreferenced variable
- fixed compilation issue with sws_..isSupported when compiling with ffmpeg 0.5
- use _AVCODECID_NONE instead of CODEC_ID_NONE
- render video using double buffers
this is to deliver frames more accurately to the client
- Arrays should be deleted using "delete[]" and not "delete"
Merge branch 'zms/videostream-improvements' of https://github.com/Sune1337/ZoneMinder into Sune1337-zms/videostream-improvements

Conflicts:
	src/zm_ffmpeg.h
	src/zm_mpeg.cpp
Merge branch 'Sune1337-zms/videostream-improvements'