Reference-count inlined functions to keep them alive until we emit debug

info for them and generally clean up the inline scope handling a bit.
Fix the debug scope handling for all clients of SILCloner, especially
the SIL-level spezializers and inliners.
This also adds a ton of additional assertions that will ensure that
future optimization passes won't mess with the debug info in a way that
could confuse the LLVM backend.

Swift SVN r18984

lib/SIL/SILModule.cpp

@@ -93,6 +93,9 @@ SILModule::SILModule(Module *SwiftModule)
 }
 
 SILModule::~SILModule() {
+  for (SILFunction *F : InlinedFunctions)
+    F->decrementRefCount();
+
   // Drop everything functions in this module reference.
   //
   // This is necessary since the functions may reference each other.  We don't