Don't risk truncating open flags by using mode_t

On Android, 32-bit arm and x86 use __kernel_mode_t (an unsigned short)
as their mode_t.  The open(2) flags are actually an int, so high ones
like O_CLOEXEC get truncated if you coerce them to mode_t.

* defs.h (tprint_open_modes, sprint_open_modes): Change argument type
from mode_t to int.
* file.c (tprint_open_modes, sprint_open_modes): Likewise.

Signed-off-by: Elliott Hughes <enh@google.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>