Rename _LIBCPP_DEBUG2 to _LIBCPP_DEBUG.

llvm-svn: 189140
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 145afa17caedb3ff6d58dfd75dd72047810190d1
diff --git a/include/vector b/include/vector
index 6a9d5a6..e4fc024 100644
--- a/include/vector
+++ b/include/vector
@@ -274,7 +274,7 @@
 
 #include <__undef_min_max>
 
-#ifdef _LIBCPP_DEBUG2
+#ifdef _LIBCPP_DEBUG
 #   include <__debug>
 #else
 #   define _LIBCPP_ASSERT(x, m) ((void)0)