[AsmParser]Emit an error if a macro has two (or more) parameters sharing the same name
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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299815
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