Implement a new command line option, -debug, which is meant to unify all of

Implement a new command line option, -debug, which is meant to unify all of
the random debugging macros scattered throughout llvm.

The new DEBUG(x) macro should be used instead of special purpose debug macros.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2709 91177308-0d34-0410-b5e6-96231b3b80d8