common,w32: Hide spawned processes by default

* common/exechelp-w32.c (gnupg_spawn_process): Use SW_HIDE
instead of SW_MINIMIZE.

Spawning minimized shows icons in the task bar so users
see that background processes are started, which is unusual.

I'm pretty sure that the intention of the code was to hide
the window if not in spawn debug mode. This is also what
GPGME does.

This fixes dirmngr_ldap process windows and other
spurious reports about e.g. a gpgv console window from
loadswdb.

• GnuPG-Bug-Id: T3937
• Signed-off-by: Andre Heinecke <aheinecke@intevation.de>