security/gnupg: add the --shared-access option to scdaemon
gnupg's scdaemon opens smart cards in exclusive mode, which prevents other
applications (such as PKCS#11 libraries) from concurrently accessing the
card). Upstream refuses to fix the problem. This commit adds a
--shared-access option to scdaemon. When enabled, scdaemon will access the
smart card in shared mode, playing nicely with other applications. The
default behavior is unchanged.