[PGO] Passmanagerbuilder change that enable IR level PGO instrumentation

This patch includes the passmanagerbuilder change that enables IR level PGO instrumentation. It adds two passmanagerbuilder options: -profile-generate=<profile_filename> and -profile-use=<profile_filename>. The new options are primarily for debug purpose.

Reviewers: davidxl, silvas

Differential Revision: http://reviews.llvm.org/D15828

llvm-svn: 258420