Make -m[no-]pascal-strings an alias of -f[no]pascal-strings in the .td file

This way we don't have to translate it manually in Clang::ConstructJob.

Differential Revision: http://llvm-reviews.chandlerc.com/D1249

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187547 91177308-0d34-0410-b5e6-96231b3b80d8