Three changes:

Three changes:
1. Introduce some enums and accessors in the InlineAsm class
   that eliminate a ton of magic numbers when handling inline
   asm SDNode.
2. Add a new MDNodeSDNode selection dag node type that holds
   a MDNode (shocking!)
3. Add a new argument to ISD::INLINEASM nodes that hold !srcloc
   metadata, propagating it to the instruction emitter, which
   drops it.

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100605 91177308-0d34-0410-b5e6-96231b3b80d8