Implement LTOModule on top of IRObjectFile.

IRObjectFile provides all the logic for producing mangled names and getting
symbols from inline assembly.

LTOModule then adds logic for linking specific tasks, like constructing
llvm.compiler_user or extracting linker options from the bitcode.

The rule of the thumb is that IRObjectFile has the functionality that is
needed by both LTO and llvm-ar.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212349 91177308-0d34-0410-b5e6-96231b3b80d8
TableGen: introduce support for MSBuiltin

Add MSBuiltin which is similar in vein to GCCBuiltin.  This allows for adding
intrinsics for Microsoft compatibility to individual instructions.  This is
needed to permit the creation of ARM specific MSVC extensions.

This is not currently in use, and requires an associated change in clang to
enable use of the intrinsics defined by this new class.  This merely sets the
LLVM portion of the infrastructure in place to permit the use of this
functionality.  A separate set of changes will enable the new intrinsics.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212350 91177308-0d34-0410-b5e6-96231b3b80d8