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/Frontend/AnalysisConsumer.cpp b/lib/Frontend/AnalysisConsumer.cpp
index 3bdd0ca..06af2d9 100644
--- a/lib/Frontend/AnalysisConsumer.cpp
+++ b/lib/Frontend/AnalysisConsumer.cpp
@@ -341,8 +341,8 @@
   if (!ObjCImplementationActions.empty()) {
     TranslationUnitDecl *TUD = C.getTranslationUnitDecl();
     
-    for (DeclContext::decl_iterator I = TUD->decls_begin(C),
-                                    E = TUD->decls_end(C);
+    for (DeclContext::decl_iterator I = TUD->decls_begin(),
+                                    E = TUD->decls_end();
          I != E; ++I)
       if (ObjCImplementationDecl* ID = dyn_cast<ObjCImplementationDecl>(*I))
         HandleCode(ID, 0, ObjCImplementationActions);