Add missing #include <string.h> in x86/cpu.c
Originally committed as revision 25088 to svn://svn.ffmpeg.org/ffmpeg/trunk
Clean up av_get_cpu_flag()
Instead of defining functions in per-arch header files includedby the main cpu.c, define them normally and call them from thegeneric one.
Originally committed as revision 25084 to svn://svn.ffmpeg.org/ffmpeg/trunk