fix build against ffmpeg >= 1.0

these commits were taken from xbmc (lib/DllAvFilter.h) :
 AvFilter wrapper: Remove unused avfilter_poll_frame which has been removed in libavfilter 3.
 AvFilter wrapper: Remove unused avfilter_request_frame mapping as the function has been removed in libavfilter 3.
 AvFilter wrapper: Remove unused avfilter_get_video_buffer mapping as the function has been removed in libavfilter 3.
 AvFilter: Map and use av_buffersrc_add_frame instead of av_vsrc_buffer_add_frame with libavfilter version 3.
Merge pull request #101 from twolife/master

fix build against ffmpeg >= 1.0
Fix sound with recent FFmpeg by converting from av_audio_convert API to the swresample one
Fix non-square pixel display apect ratio and 3D TAB modes correctly.
Make hdmi_clock_sync a default when changing hdmi mode. Make changing hdmi mode a default when requesting 3D.
Support file naming of 3DSBS/HSBS and 3DTAB/HTAB to default to 3D modes
Pick up some fixes from xbmc.
Fix h264 in avi file timestamps.
Add extra buffer when deinterlacing to avoid hanging.
Remove bitstream converter and get GPU to do it.
Experimental support for extra codecs.
Supports MJPEG, VP6, VP8 and Ogg Theora. Requires start_x.elf firmware.
external SRT subtitles; smaller, customizable, subtitle buffer size; rudimentary SSA parsing
Don't reject MJPEG as that is now supported
Merge pull request #104 from torarin/external_subtitles_plus_ssa

Subtitle improvements
Merge pull request #102 from twolife/master

Fix sound when build against FFmpeg 1.1
Fixed short option "-n" for allowing a parameter as "--aidx" do.
Merge pull request #108 from skgsergio/fix_short_aidx_option

Fixed short option "-n" which causes "Segmentation Fault"
Add command line option to set the video output window
Fix typo when rejecting invalid video destination window
Update README.md
Merge pull request #112 from torarin/patch-1

Inform of GCC 4.7 requirement in README
Handle resolution changes during video stream.

When the resolution changes, GPU sends a port settings changed message. Host has to acknowledge it by disabling and enabling the affected ports.
Default to hdmi audio if hdmi audio support is detected. Can be overridden with -o local
Allow = key to also increase volume
Remove log messages for timeout failure when timeout=0