* removes use of read_key and getchar when input is received on stdin
(this was corrupting the packet reading)
* terminates av_encode when a termination signal is received (use of
ctrl-c issued a term_exit and subsequent uses of q failed)
* specific correction to yuv4mpeg pipe reading - the defined header was
too short to allow for extended yuv4mpeg flags [as used by smil2yuv and
y4mscaler and accepted by mjpeg tools]


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@2183 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b