[ARM64] Fix up predefines, including adding big endian support to Targets.cpp

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206390 91177308-0d34-0410-b5e6-96231b3b80d8
[ARM64] Allow the disabling of NEON and crypto instructions. Update tests to pass -target-feature +neon.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206394 91177308-0d34-0410-b5e6-96231b3b80d8
[ARM64] Plumb in the -mfpu= flag.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206395 91177308-0d34-0410-b5e6-96231b3b80d8