common:w32: Care about the NUL device for start_new_service.
* common/homedir.c [HAVE_W32_SYSTEM] (gnupg_isatty): New. * common/util.h [HAVE_W32_SYSTEM] (gnupg_isatty): New. * common/asshelp.c (start_new_service): Specify GPGRT_PROCESS_STDIO_NUL.
- GnuPG-bug-id: T7716
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>