Constify the result of CFGStmt::getStmt().

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@138408 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CFGStmtMap.cpp b/lib/Analysis/CFGStmtMap.cpp
index 1fd5eed..16df676 100644
--- a/lib/Analysis/CFGStmtMap.cpp
+++ b/lib/Analysis/CFGStmtMap.cpp
@@ -19,7 +19,7 @@
 
 using namespace clang;
 
-typedef llvm::DenseMap<Stmt*,CFGBlock*> SMap;
+typedef llvm::DenseMap<const Stmt*, CFGBlock*> SMap;
 static SMap *AsMap(void *m) { return (SMap*) m; }
 
 CFGStmtMap::~CFGStmtMap() { delete AsMap(M); }