[MPlayer-users] Reduce spam in console / ffmpeg defines

[Josh]

At least in MinGW under Windows, the console keeps reminding me on every 
file that the following aren't defined for FFmpeg when compiling MPlayer:

HAVE_MM_EMPTY
HAVE_RDTSC

But to a lesser extent and not as spammy: HAVE_STRUCT_POLLFD

As far as I know they should be 0,  I ran ffmpeg configure by itself and 
grabbed the values from config.h, can't say for non-MinGW/Windows.