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/CheckObjCUnusedIVars.cpp b/lib/Analysis/CheckObjCUnusedIVars.cpp
index bbcf90e..6764985 100644
--- a/lib/Analysis/CheckObjCUnusedIVars.cpp
+++ b/lib/Analysis/CheckObjCUnusedIVars.cpp
@@ -83,14 +83,14 @@
     return;
   
   // Now scan the methods for accesses.
-  for (ObjCImplementationDecl::instmeth_iterator I = D->instmeth_begin(Ctx),
-       E = D->instmeth_end(Ctx); I!=E; ++I)
+  for (ObjCImplementationDecl::instmeth_iterator I = D->instmeth_begin(),
+       E = D->instmeth_end(); I!=E; ++I)
     Scan(M, (*I)->getBody());
   
   // Scan for @synthesized property methods that act as setters/getters
   // to an ivar.
-  for (ObjCImplementationDecl::propimpl_iterator I = D->propimpl_begin(Ctx),
-       E = D->propimpl_end(Ctx); I!=E; ++I)
+  for (ObjCImplementationDecl::propimpl_iterator I = D->propimpl_begin(),
+       E = D->propimpl_end(); I!=E; ++I)
     Scan(M, *I);  
   
   // Find ivars that are unused.