Change the name of the vtable-debugging environment variable to
CLANG_VTABLE_DEBUG.

llvm-svn: 96785
diff --git a/clang/lib/CodeGen/CGVtable.cpp b/clang/lib/CodeGen/CGVtable.cpp
index 43fd56a..97d21f3 100644
--- a/clang/lib/CodeGen/CGVtable.cpp
+++ b/clang/lib/CodeGen/CGVtable.cpp
@@ -2034,7 +2034,7 @@
   }
 
 //#define D1(x)
-#define D1(X) do { if (getenv("DEBUG")) { X; } } while (0)
+#define D1(X) do { if (getenv("CLANG_VTABLE_DEBUG")) { X; } } while (0)
 
   void GenerateVBaseOffsets(const CXXRecordDecl *RD, uint64_t Offset,
                             bool updateVBIndex, Index_t current_vbindex) {