arm: dynamic NEON support for SkBlitRow_opts_arm.cpp

This patch moves all NEON-specific code from the source
src/opts/SkBlitRow_opts_arm.cpp into a new file that is
built as part of the 'opts_arm_neon' static library.
Review URL: https://codereview.appspot.com/6449110

git-svn-id: http://skia.googlecode.com/svn/trunk@5016 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed