Added support for mcpu krait

- krait processor currently modeled with the same features as A9.
- Krait processor additionally has VFP4 (fused multiply add/sub)
and hardware division features enabled.
- krait has currently the same Schedule model as A9
- krait cpu flag is not recognized by the GNU assembler yet,
it is replaced with march=armv7-a to avoid a lower march
from being used.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196618 91177308-0d34-0410-b5e6-96231b3b80d8

Conflicts:
	lib/Basic/Targets.cpp
	lib/Driver/ToolChain.cpp
	lib/Driver/ToolChains.cpp
	lib/Driver/Tools.cpp
	test/Preprocessor/arm-target-features.c

Change-Id: I3f6840e56828be3d5a94d0b03b07961a5b9b4b9f