c++: CWG 2359, wrong copy-init with designated init [PR91319]

c++: CWG 2359, wrong copy-init with designated init [PR91319]

This CWG clarifies that designated initializer support direct-initialization.
Just be careful what Note 2 in [dcl.init.aggr]/4.2 says: "If the
initialization is by designated-initializer-clause, its form determines
whether copy-initialization or direct-initialization is performed."  Hence
this patch sets CONSTRUCTOR_IS_DIRECT_INIT only when we are dealing with
".x{}", but not ".x = {}".

	PR c++/91319

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_initializer_list): Set CONSTRUCTOR_IS_DIRECT_INIT
	when the designated initializer is of the .x{} form.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/desig30.C: New test.