Disable the "'extern' variable has an initializer" warning in C++,
since it makes sense there to have const extern variables. Fixes
PR6495.

llvm-svn: 101818
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 182a85a..045b3e8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -3818,7 +3818,8 @@
       }
     }
   } else if (VDecl->isFileVarDecl()) {
-    if (VDecl->getStorageClass() == VarDecl::Extern)
+    if (VDecl->getStorageClass() == VarDecl::Extern && 
+        !getLangOptions().CPlusPlus)
       Diag(VDecl->getLocation(), diag::warn_extern_init);
     if (!VDecl->isInvalidDecl()) {
       InitializationSequence InitSeq(*this, Entity, Kind, &Init, 1);