Try to fix a layering violation introduced by r213945

The dragonegg buildbot (and others?) started failing after
r213945/r213946 because `llvm-as` wasn't linking in the bitcode reader.
I think moving the verify functions to the same file as the verify pass
should fix the build.  Adding a command-line option for maintaining
use-list order in assembly as a drive-by to prevent warnings about
unused static functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213947 91177308-0d34-0410-b5e6-96231b3b80d8