Revert r151638 because it causes assertion hit on PCH creation for Cocoa.h

Original log:
---------------------
Correctly track tags and enum members defined in the prototype of a function, and ensure they are properly scoped.

This fixes code such as:

enum e {x, y};
int f(enum {y, x} n) {
 return 0;
}

This finally fixes PR5464 and PR5477.
---------------------

I also reverted r151641 which was enhancement on top of r151638.

llvm-svn: 151667

clang/lib/Sema/Scope.cpp

@@ -59,13 +59,3 @@ void Scope::Init(Scope *parent, unsigned flags) {
   Entity = 0;
   ErrorTrap.reset();
 }
-
-bool Scope::containedInPrototypeScope() const {
-  const Scope *S = this;
-  while (S) {
-    if (S->isFunctionPrototypeScope())
-      return true;
-    S = S->getParent();
-  }
-  return false;
-}