Nathan Myers  <ncm@cantrip.org>

        * include/bits/basic_string.h
	(assign(__str, __pos, __n), assign(__s, __n)):  Optimize
	by avoiding unnecessary temporaries.
	(assign(__s)): Call assign(__s, __n).
	* include/bits/basic_string.tcc (_M_replace_safe): Adjust comment.
	* include/bits/std_string.h: include stl_function.h.
        * testsuite/21_strings/assign.cc (test02, test03): New tests.

Co-Authored-By: Nathan Myers <ncm@cantrip.org>

From-SVN: r48053