Implement full support for non-pointer pointers in custom allocators for string. This completes the custom pointer support for the entire library.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@185167 91177308-0d34-0410-b5e6-96231b3b80d8

test/strings/basic.string/string.access/back.pass.cpp

@@ -15,6 +15,8 @@
 #include <string>
 #include <cassert>
 
+#include "../min_allocator.h"
+
 template <class S>
 void
 test(S s)
@@ -28,7 +30,16 @@ test(S s)
 
 int main()
 {
+    {
     typedef std::string S;
     test(S("1"));
     test(S("1234567890123456789012345678901234567890"));
+    }
+#if __cplusplus >= 201103L
+    {
+    typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
+    test(S("1"));
+    test(S("1234567890123456789012345678901234567890"));
+    }
+#endif
 }