Introduce global config file /etc/gnupg/scute.conf.

* configure.ac: Require libgpg-error 1.38
* src/options.h: New.
* src/readconf.c: New.
* src/Makefile.am (sources): Add them.
* src/debug.c (_scute_debug_flags): Replace by _scute_op.debug_flags.
(_scute_debug_init): Adjust accordingly.
* src/debug.h: Include options.h.  Include line number in debug
output.
* src/p11-initialize.c (C_Initialize): Read global configuration.

An example for such a config file is:

[echo begin of sys config (user=${user})]
[+verbose]
debug 3
log-file socket:///var/log/scute/scute.log

user ubi

log-file is not scurrently supported so that the value given by a
envvar SCUTE_DEBUG is still used; this will eventually be changed.

• Signed-off-by: Werner Koch <wk@gnupg.org>