Specify -mfpu=neon for neon files

Specify -mfpu=neon for neon files

Neon files with intrinsics need the extra flag. They also need other
-mfpu= flags removed. 

In order to avoid complexity, don't try to remove the OS==mac
condition in the neon intrinsic target. It is not reachable and so
safe to ignore. Also don't target the -mfpu removal. It has no
effect on x86 builds.

TBR=tomfinegan@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=247630

[Johann, 2014-01-29 05:35:20]

Committed patchset #2 manually as r247630 (presubmit successful).