C: use full locations within c_parser_expr_list's vec<location_t>

C: use full locations within c_parser_expr_list's vec<location_t>

The previous patch uncovered a bug in how c_parser_expr_list builds the
vec<location_t>: it was only using the location of the first token
within each assignment-expression in the expr-list.

This shows up in e.g. this -Wformat warning, where only part of the
2nd param is underlined:

   printf("hello %i", (long)0);
                 ~^   ~
                 %li

This patch fixes c_parser_expr_list to use the full range of
each assignment-expression in the list for the vec<location_t>, so
that for the above we print:

   printf("hello %i", (long)0);
                 ~^   ~~~~~~~
                 %li

gcc/c/ChangeLog:
	* c-parser.c (c_parser_expr_list): Use c_expr::get_location ()
	rather than peeking the location of the first token.
	* c-tree.h (c_expr::get_location): New method.

gcc/testsuite/ChangeLog:
	* gcc.dg/format/diagnostic-ranges.c (test_mismatching_types):
	Update expected result to show all of "(long)0" being underlined.
	* gcc.dg/plugin/diagnostic-test-string-literals-1.c
	(test_multitoken_macro): Update expected underlining.

From-SVN: r251239