[gentoo-dev] New global USE flag "neon" for ARM NEON optimization(s)

[Samuli Suominen]

i'll add USE=neon to use.desc and punt the local descriptions if nobody 
objects

media-libs/libpng: support ARM NEON cpu instruction set
media-libs/vo-aacenc: Enable neon cpu instructions
media-video/ffmpeg: Enables NEON optimizations for arm processors.
media-video/libav: Enable NEON optimizations for arm processors.
media-video/vlc: Enables NEON optimizations for arm processors.
x11-libs/pixman: Enables NEON optimizations for ARM processors.