* agent/command.c (cmd_pksign): Change var name 'rc' to 'err'.
* agent/findkey.c (read_key_file): Ditto.  Change return type to
gpg_error_t.  On es_fessk failure return a correct error code.
(agent_key_from_file): Change var name 'rc' to 'err'.
* agent/pksign.c (agent_pksign_do): Ditto.  Change return type to
gpg_error_t.  Return a valid erro code on malloc failure.
(agent_pksign): Ditto.  Change return type to gpg_error_t.  replace
xmalloc by xtrymalloc.
* agent/protect.c (calculate_mic): Change return type to gpg_error_t.
(do_decryption): Ditto.  Do not init RC.
(merge_lists): Change return type to gpg_error_t.
(agent_unprotect): Ditto.
(agent_get_shadow_info): Ditto.