[mips] Add new error message and improve testing for parsing the .module directive.

Summary:
We used to silently ignore any empty .module's and we used to give an error saying that we found
an "unexpected token at start of statement" when the value of the option wasn't an identifier (e.g. if it was a number).

We now give an error saying that we "expected .module option identifier" in both of those cases.

I also fixed the other tests in mips-abi-bad.s, which all seemed to be broken.


Reviewers: dsanders

Reviewed By: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D7095

llvm-svn: 226905