Refactor and clean up a bunch more code. No major functionality changes.

 * Make several methods of bugdriver global functions (ParseInputFile, PrintFunctionList)
 * Make PrintFunctionList truncate the output after 10 entries, like the crash debugger
   did.  This allows code sharing.
 * Add a couple of methods to BugDriver that allows us to eliminate some friends
 * Improve comments in ExtractFunction.cpp
 * Make classes that used to be friends up bugdriver now live in anon namespaces
 * Rip a bunch of functionality in the miscompilation tester into a new
   TestMergedProgram function for future code sharing.
 * Fix a bug in the miscompilation tester induced in my last checkin

llvm-svn: 12393