[x264-devel] drop support for nasm-0.98

[Loren Merritt]

I plan to drop support for nasm < 2.0 soon, in order to eliminate a bunch 
of SSE3 related ifdefs. You all should be using yasm anyway, but if 
someone strenuously objects maybe I can come up with a way to isolate the 
kludge in one place. Not that I expect it; nasm build seems to have been 
broken for a while already, and I haven't heard many complaints.

--Loren Merritt