start_stop_daemon: add -chuid support

include/libbb.h

@@ -443,7 +443,10 @@ struct bb_uidgid_t {
 	uid_t uid;
 	gid_t gid;
 };
+/* always sets uid and gid */
 int get_uidgid(struct bb_uidgid_t*, const char*, int numeric_ok);
+/* chown-like handling of "user[:[group]" */
+void parse_chown_usergroup_or_die(struct bb_uidgid_t *u, char *user_group);
 /* what is this? */
 /*extern char *bb_getug(char *buffer, char *idname, long id, int bufsize, char prefix);*/
 char *bb_getpwuid(char *name, long uid, int bufsize);

include/usage.h

@@ -2893,7 +2893,7 @@
        "\n	-N|--nicelevel <N>		Add N to process's nice level" \
 	) \
        "\n	-s|--signal <signal>		Signal to send (default TERM)" \
-       "\n	-U|--chuid <username>|<uid>	Start process with this name"
+       "\n	-c|--chuid <user>[:[<group>]]	Change to specified user/group"
 
 #define stat_trivial_usage \
        "[OPTION] FILE..."