time-picker: Prefer g_auto* macros

g_autofree will automatically free variables when they go out of
scope. g_autoptr will do the same, but using the appropriate freefunc
for the given type, e.g. GDateTime -> g_date_time_unref() or
GObject -> g_object_unref().

This automatic cleanup reduces the risk of memory leaks
and allows getting rid of some lines of code.

src/time-picker/time-picker.c

@@ -53,10 +53,9 @@ void
 time_picker_set_time_zone (TimePicker *time_picker,
                            double      time_zone)
 {
-  char *char_time_zone;
+  g_autofree char *char_time_zone = NULL;
   char_time_zone = g_strdup_printf ("UTC %s%.1f", time_zone>=0 ? "+" : "", time_zone);
   gtk_label_set_text (GTK_LABEL (time_picker->label_time_zone), char_time_zone);
-  g_free (char_time_zone);
 }
 
 
@@ -135,7 +134,7 @@ static gboolean
 time_spin_button_text (GtkSpinButton *self)
 {
   int value;
-  char *button_text;
+  g_autofree char *button_text = NULL;
   GtkAdjustment *adjustment;
 
   adjustment = gtk_spin_button_get_adjustment (self);
@@ -143,7 +142,6 @@ time_spin_button_text (GtkSpinButton *self)
   button_text = g_strdup_printf ("%02d", value);
   gtk_editable_set_text (GTK_EDITABLE (self),
                          button_text);
-  g_free (button_text);
 
   return TRUE;
 }
@@ -156,9 +154,9 @@ static void
 day_selected (GtkCalendar         *self,
               TimePicker          *time_picker)
 {
-  GDateTime *date_selected;
+  g_autoptr (GDateTime) date_selected = NULL;
   GtkPopover *popover;
-  char *button_text;
+  g_autofree char *button_text = NULL;
 
   (void) self;
   date_selected = gtk_calendar_get_date (GTK_CALENDAR (time_picker->calendar));
@@ -181,9 +179,6 @@ day_selected (GtkCalendar         *self,
   popover = GTK_POPOVER(time_picker->calendar_popover);
   gtk_popover_popdown (popover);
 
-  g_free (button_text);
-  g_date_time_unref (date_selected);
-
   input_changed (GTK_WIDGET (self), time_picker);
 }