PR fortran/16404

PR fortran/16404
(parts ported from g95)
* parse.h (gfc_state_data): New field do_variable.
(gfc_check_do_variable): Add prototype.
* parse.c (push_state): Initialize field 'do_variable'.
(gfc_check_do_variable): New function.
(parse_do_block): Remember do iterator variable.
(parse_file): Initialize field 'do_variable'.
* match.c (gfc_match_assignment, gfc_match_do,
gfc_match_allocate, gfc_match_nullify, gfc_match_deallocate):
Add previously missing checks.
(gfc_match_return): Reformat error message.
* io.c (match_out_tag): New function.
(match_open_element, match_close_element,
match_file_element, match_dt_element): Call match_out_tag
instead of match_vtag where appropriate.
(match_io_iterator, match_io_element): Add missing check.
(match_io): Reformat error message.
(match_inquire_element): Call match_out_tag where appropriate.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@84793 138bc75d-0d04-0410-961f-82ee72b054a4