This patch is to move GlobalMerge pass from Transform/Scalar
to CodeGen, because GlobalMerge depends on TargetMachine.
In the mean time, the macro INITIALIZE_TM_PASS is also moved
to CodeGen/Passes.h. With this fix we can avoid making
libScalarOpts depend on libCodeGen.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210951 91177308-0d34-0410-b5e6-96231b3b80d8