Use gfc_charlen_type instead of int for string lenghts

Use gfc_charlen_type instead of int for string lenghts

This patch cleans up a few places where I noticed the code was still
using int instead gfc_charlen_type for string lengths.  Regtested on
x86_64-pc-linux-gnu, committed as obvious.

libgfortran/ChangeLog:

2018-10-06  Janne Blomqvist  <jb@gcc.gnu.org>

	* io/unix.c (compare_file_filename): Use gfc_charlen_type instead
	of int for string length.
	(inquire_sequential): Likewise.
	(inquire_direct): Likewise.
	(inquire_formatted): Likewise.
	(inquire_unformatted): Likewise.
	(inquire_access): Likewise.
	(inquire_read): Likewise.
	(inquire_write): Likewise.
	(inquire_readwrite): Likewise.
	* io/unix.h (compare_file_filename): Likewise.
	(inquire_sequential): Likewise.
	(inquire_direct): Likewise.
	(inquire_formatted): Likewise.
	(inquire_unformatted): Likewise.
	(inquire_read): Likewise.
	(inquire_write): Likewise.
	(inquire_readwrite): Likewise.

From-SVN: r264901