Inconsistency wrt Allocators in basic_string assignment (LWG2579)

Inconsistency wrt Allocators in basic_string assignment (LWG2579)

2019-05-14  Nina Dinka Ranns  <dinka.ranns@gmail.com>

	Inconsistency wrt Allocators in basic_string assignment (LWG2579)
	* include/bits/basic_string.h: (operator=(const basic_string&):
	Move allocator decision to assign.
	(assign(const basic_string&)): Move allocator decision here.
	* testsuite/21_strings/basic_string/allocator/char/copy_assign.cc:
	Add tests.
	* testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc:
	Add tests.

From-SVN: r271165