* c-common.c (scan_char_table): Add 'w' to flags for all formats
	except 'n'.
	(check_format_info): Set 'wide' for scanf format widths.  Warn for
	a zero scanf width.  Make the check for writing into a constant
	object at the first level of indirection; at later levels, warn if
	any type qualifiers are encountered.

testsuite:
	* gcc.dg/c90-scanf-1.c, gcc.dg/c94-scanf-1.c: New tests.

From-SVN: r35842