Basic: add support for ARM ACLE 6.5.1

Extend ARM ACLE support (Section 6.5.1) for AArch32.  Define __ARM_FP if
hardware floating point support is available as per the value defined by the
ACLE.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217957 91177308-0d34-0410-b5e6-96231b3b80d8