CodeGen: rename __builtin_arm_sevl to __sevl

ACLE adds the __sevl() extension.  Rename the hint from a custom name to the
ACLE specified name.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@207829 91177308-0d34-0410-b5e6-96231b3b80d8
CodeGen: reorder ARM hint

__yield is part of the ACLE specified extensions and not specific to MSVC.
Move the declaration for the hint to the proper group.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@207830 91177308-0d34-0410-b5e6-96231b3b80d8