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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@151667 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/IdentifierResolver.cpp b/lib/Sema/IdentifierResolver.cpp
index 2183231..b469161 100644
--- a/lib/Sema/IdentifierResolver.cpp
+++ b/lib/Sema/IdentifierResolver.cpp
@@ -113,7 +113,7 @@
                              bool ExplicitInstantiationOrSpecialization) const {
   Ctx = Ctx->getRedeclContext();
 
-  if (Ctx->isFunctionOrMethod() || S->isFunctionPrototypeScope()) {
+  if (Ctx->isFunctionOrMethod()) {
     // Ignore the scopes associated within transparent declaration contexts.
     while (S->getEntity() &&
            ((DeclContext *)S->getEntity())->isTransparentContext())