flv: Improve log messages

Messages should start with a capital letter and possibly end with a "."
if they are statements.
flv: Warn only once

No point in sending the message multiple time.
flv: Do not mangle dts values for negative cts

Some applications really mean to send negative pts.
Merge commit '374fdc8c071dcd96422378b0a1a0d453336d8a01'

* commit '374fdc8c071dcd96422378b0a1a0d453336d8a01':
  flv: Improve log messages

Conflicts:
	libavformat/flvdec.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '5d983fdbca5570a1545a892583a372cfb3fffe92'

* commit '5d983fdbca5570a1545a892583a372cfb3fffe92':
  flv: Warn only once

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '152b797cd687e96a582a1cb908dddf3d330d7637'

* commit '152b797cd687e96a582a1cb908dddf3d330d7637':
  flv: Do not mangle dts values for negative cts

Merged-by: Michael Niedermayer <michaelni@gmx.at>
fate: Add fic-in-avi test

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
x86/mpegaudiodsp: define apply_window_mp3 as SSE

None of the handwritten asm in this function seems to be SSE2

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>