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



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@86638 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index a6b0dfb..bb3559b 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -258,7 +258,7 @@
 
 UnresolvedUsingDecl *
 ASTContext::getInstantiatedFromUnresolvedUsingDecl(UsingDecl *UUD) {
-  llvm::DenseMap<UsingDecl *, UnresolvedUsingDecl *>::iterator Pos
+  llvm::DenseMap<UsingDecl *, UnresolvedUsingDecl *>::const_iterator Pos
     = InstantiatedFromUnresolvedUsingDecl.find(UUD);
   if (Pos == InstantiatedFromUnresolvedUsingDecl.end())
     return 0;