constify methods.

llvm-svn: 76873
diff --git a/clang/lib/Index/Entity.cpp b/clang/lib/Index/Entity.cpp
index c7924f6..25061e6 100644
--- a/clang/lib/Index/Entity.cpp
+++ b/clang/lib/Index/Entity.cpp
@@ -156,7 +156,7 @@
   return Val.get<EntityImpl *>()->getDecl(AST);
 }
 
-std::string Entity::getPrintableName() {
+std::string Entity::getPrintableName() const {
   if (isInvalid())
     return "<< Invalid >>";