Revert "Tooling/ReplacementsYaml.h: Prune Tooling's llvm::yaml::ScalarTraits<std::string> corresponding to LLVM r193344."

This reverts commit r193350, because it addressed an llvm API change that has been reverted.
ARM: Mark double-precision instructions as such

This prevents us from silently accepting invalid instructions on (for example)
Cortex-M4 with just single-precision VFP support.

No tests for the extra Pat Requires because they're essentially assertions: the
affected code should have been lowered to libcalls before ISel.

rdar://problem/15302004