* include/bits/basic_string.h (c_str()): Simplify, due to
	21.3.4 the internal representation is always kept null-terminated.
	* include/bits/basic_string.tcc (_M_clone): Null-terminate.
	* testsuite/21_strings/basic_string/element_access/char/4.cc: New.
	* testsuite/21_strings/basic_string/element_access/wchar_t/4.cc: Ditto.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@76092 138bc75d-0d04-0410-961f-82ee72b054a4