Workaround for MacOSX build failure with gcc <= 4.4

Summary:
A better solution to http://llvm.org/bugs/show_bug.cgi?id=13777
Named namespace + more unique name to make ODR violations unlikely.

Reviewers: chandlerc, doug.gregor, klimek

Reviewed By: doug.gregor

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D38

llvm-svn: 163513