FLV handling for VP6 with alpha channel, FLV h264 height may be incorrect

Merging changes contributed by Xander Schouwerwou:

"When I was testing several flv video files, I found some issues:

- The decoding for GETID3_FLV_VIDEO_VP6FLV_ALPHA was missing. If you try
to get info from a file without meta data it cannot find the width &
height.

- In the h264 decoding I got incorrect dimensions from the h264_bug.flv
[supplied sample file] has a H264_PROFILE_BASELINE encoding. The height
was 8 pixels off. I rewrote the readData function.

Reference:

http://stackoverflow.com/questions/6394874/fetching-the-dimensions-of-a-h264video-stream
http://multimedia.cx/mirror/vp6_format.pdf

http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-H.264-200305-S!!PDF-E&type=items
"