Make Record Name an Init

Make Record Name an Init

Use an Init (ultimately a StringInit) to represent the Record name.
This allows the name to be composed by standard TableGen operators.
This will enable us to get rid of the ugly #NAME# hack processing and
naturally replace it with operators.  It also increases flexibility
and power of the TableGen language by allowing record identifiers to
be computed dynamically.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137232 91177308-0d34-0410-b5e6-96231b3b80d8