Add optional profile counts to block frequency dump.

Summary:
Print profile counts as the third value in addition to the existing 'float' and
the 'int' values in the textual block frequency dump, if available.

Reviewers: davidxl

Reviewed By: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37835

llvm-svn: 313220