De-ASTContext-ify DeclContext.

Remove ASTContext parameter from DeclContext's methods. This change cascaded down to other Decl's methods and changes to call sites started "escalating".
Timings using pre-tokenized "cocoa.h" showed only a ~1% increase in time run between and after this commit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74506 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CheckObjCInstMethSignature.cpp b/lib/Analysis/CheckObjCInstMethSignature.cpp
index 9fec7c1..2881486 100644
--- a/lib/Analysis/CheckObjCInstMethSignature.cpp
+++ b/lib/Analysis/CheckObjCInstMethSignature.cpp
@@ -86,8 +86,8 @@
   MapTy IMeths;
   unsigned NumMethods = 0;
   
-  for (ObjCImplementationDecl::instmeth_iterator I=ID->instmeth_begin(Ctx),
-       E=ID->instmeth_end(Ctx); I!=E; ++I) {    
+  for (ObjCImplementationDecl::instmeth_iterator I=ID->instmeth_begin(),
+       E=ID->instmeth_end(); I!=E; ++I) {    
     
     ObjCMethodDecl* M = *I;
     IMeths[M->getSelector()] = M;
@@ -97,8 +97,8 @@
   // Now recurse the class hierarchy chain looking for methods with the
   // same signatures.
   while (C && NumMethods) {
-    for (ObjCInterfaceDecl::instmeth_iterator I=C->instmeth_begin(Ctx),
-         E=C->instmeth_end(Ctx); I!=E; ++I) {
+    for (ObjCInterfaceDecl::instmeth_iterator I=C->instmeth_begin(),
+         E=C->instmeth_end(); I!=E; ++I) {
 
       ObjCMethodDecl* M = *I;
       Selector S = M->getSelector();