libgfortran: Fix -Wincompatible-pointer-types errors

As reported, libgfortran fails to build on targets where int32_t and int
are different types, because it uses int vs. GFC_INTEGER_4 (under hood
int32_t) interchangeably.

The following patch fixes that.

2023-12-05  Florian Weimer  <fweimer@redhat.com>
	    Jakub Jelinek  <jakub@redhat.com>

	* io/list_read.c (list_formatted_read_scalar) <case BT_CLASS>:
	Change types of unit and noiostat to GFC_INTEGER_4 from int, change
	type of child_iostat from to GFC_INTEGER_4 * from int *, formatting
	fixes.
	(nml_read_obj): Likewise.
	* io/write.c (list_formatted_write_scalar) <case BT_CLASS>: Likewise.
	(nml_write_obj): Likewise.
	* io/transfer.c (unformatted_read, unformatted_write): Likewise.