Introducing a new error to macro parameters' parsing:
currently, llvm-mc won't complain if a macro have two (or more) named params with the same name.
this behavior is false, as there's no merit in having some params sharing a name.
now, instead of tolerate such a phenomena - emit an appropriate error.
Differential Revision: https://reviews.llvm.org/D31674
llvm-svn: 299815
Coby Tayree