Rename _LIBCPP_DEBUG2 to _LIBCPP_DEBUG.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@189140 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/strings/basic.string/string.access/back.pass.cpp b/test/strings/basic.string/string.access/back.pass.cpp
index 9c4800e..ed0d327 100644
--- a/test/strings/basic.string/string.access/back.pass.cpp
+++ b/test/strings/basic.string/string.access/back.pass.cpp
@@ -12,7 +12,7 @@
 // const charT& back() const;
 //       charT& back();
 
-#ifdef _LIBCPP_DEBUG2
+#ifdef _LIBCPP_DEBUG
 #define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
 #endif
 
@@ -46,7 +46,7 @@
     test(S("1234567890123456789012345678901234567890"));
     }
 #endif
-#ifdef _LIBCPP_DEBUG2
+#ifdef _LIBCPP_DEBUG
     {
         std::string s;
         char c = s.back();