clang: substitute fpu neon-vfp[3|4] for fpu neon

Clang does not natively support the neon-vfp option
so we will substitute it for neon.
This allows neon-vfp to be set for gcc, and won't cause
clang to error out.

Clang will enable neon and a vfp automatically with supported
cpu's.
Do not set fpu to vfp[3|4] as this may remove neon

Change-Id: I21615d4bd156d24f4e4870c1021c46e74e0d3389
Merge commit 'refs/changes/56/16456/3' of https://gerrit.slimroms.net/SlimRoms/android_build into lp5.0