[PM] Push the debug option for the new pass manager into the opt tool

and expose the necessary hooks in the API directly.

This makes it much cleaner for example to log the usage of a pass
manager from a library. It also makes it more obvious that this
functionality isn't "optional" or "asserts-only" for the pass manager.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225841 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/PassManager.cpp

@@ -12,11 +12,6 @@
 #include "llvm/IR/PassManager.h"
 
 using namespace llvm;
-using llvm::detail::DebugPM;
-
-cl::opt<bool> llvm::detail::DebugPM(
-    "debug-pass-manager", cl::Hidden,
-    cl::desc("Print pass management debugging information"));
 
 char FunctionAnalysisManagerModuleProxy::PassID;