Refactor all of the "splitting a module into two pieces" code to avoid

Refactor all of the "splitting a module into two pieces" code to avoid
code duplication.  Also, don't use ReduceMiscompilingFunctions::TestFuncs
to print out the final message.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12387 91177308-0d34-0410-b5e6-96231b3b80d8