llvm-mc/AsmParser: Add hack to ignore Int_* and *_Int instructions for now, to

llvm-mc/AsmParser: Add hack to ignore Int_* and *_Int instructions for now, to
make it easier to see interesting ambiguities.
 - Also, check that user doesn't try to redefine the super class. This is a wart
   in the current design, in that assembler match classes aren't explicitly
   declared somewhere (so there isn't a unique place to declare the super
   class). This should probably be fixed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78532 91177308-0d34-0410-b5e6-96231b3b80d8