c++: Improve errors parsing a braced list [PR101232]

c++: Improve errors parsing a braced list [PR101232]

	PR c++/101232

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_postfix_expression): Commit to the
	parse in case we know its either a cast or invalid syntax.
	(cp_parser_braced_list): Add a heuristic to inform about
	missing comma or operator.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist-err1.C: New test.
	* g++.dg/cpp0x/initlist-err2.C: New test.
	* g++.dg/cpp0x/initlist-err3.C: New test.

Signed-off-by: Franciszek Witt <franek.witt@gmail.com>