Filtering IR printing for print-after-all/print-before-all

Summary:
This patch implements "-print-funcs" option to support function filtering for IR printing like -print-after-all, -print-before etc.
Examples:
  -print-after-all -print-funcs=foo,bar

Reviewers: mcrosier, joker.eph

Subscribers: tejohnson, joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D15776

llvm-svn: 256952