Constify.

llvm-svn: 108800
diff --git a/clang/lib/Checker/GRCoreEngine.cpp b/clang/lib/Checker/GRCoreEngine.cpp
index df790e3..87127f0 100644
--- a/clang/lib/Checker/GRCoreEngine.cpp
+++ b/clang/lib/Checker/GRCoreEngine.cpp
@@ -459,7 +459,7 @@
     Eng.WList->Enqueue(Succ, B, Idx+1);
 }
 
-ExplodedNode* GRStmtNodeBuilder::MakeNode(ExplodedNodeSet& Dst, Stmt* S, 
+ExplodedNode* GRStmtNodeBuilder::MakeNode(ExplodedNodeSet& Dst, const Stmt* S, 
                                           ExplodedNode* Pred, const GRState* St,
                                           ProgramPoint::Kind K) {
   const GRState* PredState = GetState(Pred);