Fix clang's use of DenseMap iterators after r86636 fixed their constness.
Patch by Victor Zverovich!

llvm-svn: 86638
diff --git a/clang/lib/Analysis/RegionStore.cpp b/clang/lib/Analysis/RegionStore.cpp
index 45c4228..8106260 100644
--- a/clang/lib/Analysis/RegionStore.cpp
+++ b/clang/lib/Analysis/RegionStore.cpp
@@ -164,7 +164,7 @@
   ~RegionStoreSubRegionMap() {}
 
   bool iterSubRegions(const MemRegion* Parent, Visitor& V) const {
-    Map::iterator I = M.find(Parent);
+    Map::const_iterator I = M.find(Parent);
 
     if (I == M.end())
       return true;