[CFLAA] Be more aggressive with interprocedural analysis.

This patch makes us perform interprocedural analysis on functions that
don't have internal linkage. It also removes a test that should've been
deleted in an earlier commit (since other tests now cover everything
that the newly-removed test covers).

Patch by Jia Chen.

Differential Revision: http://reviews.llvm.org/D21513

llvm-svn: 273229