Rename some functions for consistency.

Every other function in Redeclarable.h was using Decl instead of Declaration.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192900 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 7682efc..96ae437 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -1663,7 +1663,7 @@
 
   // Must be in an extern "C" context. Entities declared directly within
   // a record are not extern "C" even if the record is in such a context.
-  const SomeDecl *First = D->getFirstDeclaration();
+  const SomeDecl *First = D->getFirstDecl();
   if (First->getDeclContext()->isRecord() || !First->isInExternCContext())
     return;