[SourceKit] Refactor parameter printing to use its own callbacks NFC

The current approach of visiting the param decl won't work when we want
to visit the parameters of function *types*, or when visiting tuple
elements (which aren't themselves decls).

rdar://problem/24292226

lib/IDE/ModuleInterfacePrinting.cpp

@@ -85,6 +85,13 @@ private:
     return OtherPrinter.printSynthesizedExtensionPost(ED, NTD);
   }
 
+  void printParameterPre(PrintParameterKind Kind) override {
+    return OtherPrinter.printParameterPre(Kind);
+  }
+  void printParameterPost(PrintParameterKind Kind) override {
+    return OtherPrinter.printParameterPost(Kind);
+  }
+
   void printNamePre(PrintNameContext Context) override {
     return OtherPrinter.printNamePre(Context);
   }