(GPGME::Key#usable_for?): New method. (GPGME::SubKey#usable_for?): New method. (GPGME::sign, GPGME::encrypt): Use it.
(GPGME::Key#usable_for?): New method.
(GPGME::SubKey#usable_for?): New method.
(GPGME::sign, GPGME::encrypt): Use it.


ueno/ruby-gpgme,ueno/ruby-gpgme,ueno/ruby-gpgme