g13: Implement --umount for dm-crypt.
* g13/g13.c (main): Implement command --umount. * g13/mount.c (g13_umount_container): use the syshelper if needed. * g13/backend.c (be_umount_container): New. * g13/be-dmcrypt.c (be_dmcrypt_umount_container): New. * g13/call-syshelp.c (call_syshelp_run_umount): New. * g13/sh-cmd.c (cmd_umount): New. (register_commands): Register UMOUNT. * g13/sh-dmcrypt.c (sh_dmcrypt_umount_container): New.
- Signed-off-by: Werner Koch <wk@gnupg.org>