* src/argparse.c (opttable_t): Add new flags forced, ignore, and
explicit_ignore.
(struct _gpgrt_argparse_internal_s): Change flags to bitflags.  Add
several flags to support meta commands.
(initialize): Clear them.
(handle_meta_user): Use the new verbose flag.
(handle_meta_force): Implement.
(handle_meta_ignore): Implement.
(handle_meta_echo): Support "-echo".
(handle_meta_verbose): New.
(handle_metacmd): New meta command verbose.  Add always flag and move
the detection of unexpected meta commands to here.
(_gpgrt_argparse): Make use of the ignore and forced meta commands.
(finish_read_sys): New.
(_gpgrt_argparser): Support the verbose flag.  Call finish_read_sys.
(arg_parse): Ignore non-explicit ignored and all forced options.
* tests/t-argparse.c (main): Fix printing of the ARGPARSE_CONFFILE
case.  New option 'M'.
* tests/t-argparse.conf, tests/etc/t-argparse.conf: Various changes to
test the new meta commands.