Print the name of the generic function for a specialized function

When debug printing for a function is turned on with
-sil-print-function, print the generic function is was derived from.

Author: meg-gupta

lib/SILOptimizer/PassManager/PassManager.cpp

@@ -754,6 +754,10 @@ void SILPassManager::addFunctionToWorklist(SILFunction *F,
 
   int NewLevel = 1;
   if (DerivedFrom) {
+    if (!functionSelectionEmpty() && isFunctionSelectedForPrinting(F)) {
+      llvm::dbgs() << F->getName() << " was derived from "
+                   << DerivedFrom->getName() << "\n";
+    }
     // When SILVerifyAll is enabled, individual functions are verified after
     // function passes are run upon them. This means that any functions created
     // by a function pass will not be verified after the pass runs. Thus