wks: Allow reading of --install-key arguments from stdin.
* tools/wks-util.c (install_key_from_spec_file): New. (wks_cmd_install_key): Call it. * tools/gpg-wks-client.c (main): Allow --install-key w/o arguments. * tools/gpg-wks-server.c (main): Ditto.
- Signed-off-by: Werner Koch <wk@gnupg.org>