Rename _LIBCPP_DEBUG2 to _LIBCPP_DEBUG.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@189140 91177308-0d34-0410-b5e6-96231b3b80d8

test/strings/basic.string/string.modifiers/string_insert/iter_iter_iter.pass.cpp

@@ -12,7 +12,7 @@
 // template<class InputIterator>
 //   iterator insert(const_iterator p, InputIterator first, InputIterator last);
 
-#if _LIBCPP_DEBUG2 >= 1
+#if _LIBCPP_DEBUG >= 1
 #define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
 #endif
 
@@ -127,7 +127,7 @@ int main()
          S("12345678901234567890ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"));
     }
 #endif
-#if _LIBCPP_DEBUG2 >= 1
+#if _LIBCPP_DEBUG >= 1
     {
         std::string v;
         std::string v2;