[Patch] Simple tweak to string::_Rep::_S_create

[Benjamin Kosnik]

>	* include/ext/array_allocator.h (allocate): Fix bad_alloc check.
>	* testsuite/ext/array_allocator/2.cc: Fix wrt 64-bit archs (in
>	that case sizeof(_Rep) == 24)

Doh! Thanks for fixing this up.

-benjamin