Remove Gnome Clock location provider

This was basically a hack that happened to work because the Gnome Clock
applet could store the current location of the user, and Redshift was able
to fetch this location through GConf. Since Redshift for some time now has
supported a config file where the location can be set, there is not really
any reason to use an external, fragile solution to do the same.

src/redshift.c

@@ -68,10 +68,6 @@
 
 #include "location-manual.h"
 
-#ifdef ENABLE_GNOME_CLOCK
-# include "location-gnome-clock.h"
-#endif
-
 #ifdef ENABLE_GEOCLUE
 # include "location-geoclue.h"
 #endif
@@ -146,9 +142,6 @@ static const gamma_method_t gamma_methods[] = {
 /* Union of state data for location providers */
 typedef union {
 	location_manual_state_t manual;
-#ifdef ENABLE_GNOME_CLOCK
-	location_gnome_clock_state_t gnome_clock;
-#endif
 #ifdef ENABLE_GEOCLUE
 	location_geoclue_state_t geoclue;
 #endif
@@ -170,20 +163,6 @@ static const location_provider_t location_providers[] = {
 		(location_provider_get_location_func *)
 		location_geoclue_get_location
 	},
-#endif
-#ifdef ENABLE_GNOME_CLOCK
-	{
-		"gnome-clock",
-		(location_provider_init_func *)location_gnome_clock_init,
-		(location_provider_start_func *)location_gnome_clock_start,
-		(location_provider_free_func *)location_gnome_clock_free,
-		(location_provider_print_help_func *)
-		location_gnome_clock_print_help,
-		(location_provider_set_option_func *)
-		location_gnome_clock_set_option,
-		(location_provider_get_location_func *)
-		location_gnome_clock_get_location
-	},
 #endif
 	{
 		"manual",