Use the new x86inc features to support 64-bit Windows on all non-x264 nasm
assembly code as well.
Patch by John Adcock, dscaler.johnad AT googlemail DOT com.
Win64 changes originally by Anton Mitrofanov.
x86util changes mostly by Holger Lubitz.

Originally committed as revision 19580 to svn://svn.ffmpeg.org/ffmpeg/trunk