Refactor grep mode

Split io_save_{apts,todo}() into functions that write raw data to a file
and functions that write formatted items to stdout such that one can
easily extend the grep mode for format string support in a follow-up
commit.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

src/utils.c

@@ -485,6 +485,7 @@ long update_time_in_date(long date, unsigned hr, unsigned mn)
 	localtime_r(&t, &lt);
 	lt.tm_hour = hr;
 	lt.tm_min = mn;
+	lt.tm_sec = 0;
 	new_date = mktime(&lt);
 	EXIT_IF(new_date == -1, _("error in mktime"));