Allow assemblers with a slightly different syntax to use
the optimized neon routines.

Removed extra constraints on the calling of the optimized
routines.  All neon routines can load unaligned and handle
odd widths.

Align allocated buffers in rotate_test.cc

Add neon rotate file to gyp file for arm targets.
Review URL: http://webrtc-codereview.appspot.com/253007

git-svn-id: http://libyuv.googlecode.com/svn/trunk@59 16f28f9a-4ce2-e073-06de-1de4eb20be90