core: Implement meta command [user] for the arg parser.
* src/sysutils.c (_gpgrt_getusername): New. * src/argparse.c (struct _gpgrt_argparse_internal_s): New flags user_* and store the current user. (initialize): Free new malloced field. Clear new flags. (handle_meta_user): Implement. (handle_metacmd): Implement user sections. Remove "group" meta command. (_gpgrt_argparse): Implement user sections. (finish_read_sys): Reset new vars.
Implementing group would be somewhat complicated and it is doubtful
whether this really makes sense and is manageable for the admin.
Note that we have not yet implemented this for Windows.
- Signed-off-by: Werner Koch <wk@gnupg.org>