This adds configure and runtime checks for AVX support on x86 CPUs.
Signed-off-by: NMans Rullgard <mans@mansr.com>

Instead of defining functions in per-arch header files included
by the main cpu.c, define them normally and call them from the
generic one.

Originally committed as revision 25084 to svn://svn.ffmpeg.org/ffmpeg/trunk

function and rename it to av_get_cpu_flags().

Originally committed as revision 25076 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 25047 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 25046 to svn://svn.ffmpeg.org/ffmpeg/trunk

symbols, and move them from libavcodec/avcodec.h to libavutil/cpu.h.

Originally committed as revision 25040 to svn://svn.ffmpeg.org/ffmpeg/trunk