Add const to debug hook...

llvm-svn: 42025
diff --git a/clang/AST/Decl.cpp b/clang/AST/Decl.cpp
index ee5b0739..d457800 100644
--- a/clang/AST/Decl.cpp
+++ b/clang/AST/Decl.cpp
@@ -33,7 +33,7 @@
 
 static bool StatSwitch = false;
 
-const char *Decl::getDeclKindName() {
+const char *Decl::getDeclKindName() const {
   switch (DeclKind) {
   default: assert(0 && "Unknown decl kind!");
   case Typedef: