[libchamplain] Add missing deprecated docstring

[Jiří Techet <jiritechet src gnome org>]

commit 190079883b879679e7a9e17b911023703ff113dd
Author: Jiří Techet <techet gmail com>
Date:   Sat Jul 16 19:11:37 2016 +0200

    Add missing deprecated docstring

 champlain/champlain-0.12.vapi            |    1 +
 champlain/champlain-map-source-factory.h |    4 ++++
 2 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/champlain/champlain-0.12.vapi b/champlain/champlain-0.12.vapi
index 5d64dde..f2f0cc6 100644
--- a/champlain/champlain-0.12.vapi
+++ b/champlain/champlain-0.12.vapi
@@ -635,6 +635,7 @@ namespace Champlain {
        [Deprecated]
        public const string MAP_SOURCE_OAM;
        [CCode (cheader_filename = "champlain/champlain.h", cname = "CHAMPLAIN_MAP_SOURCE_OSM_AERIAL_MAP")]
+       [Deprecated]
        public const string MAP_SOURCE_OSM_AERIAL_MAP;
        [CCode (cheader_filename = "champlain/champlain.h", cname = "CHAMPLAIN_MAP_SOURCE_OSM_CYCLE_MAP")]
        public const string MAP_SOURCE_OSM_CYCLE_MAP;
diff --git a/champlain/champlain-map-source-factory.h b/champlain/champlain-map-source-factory.h
index a75bf15..ee6d67b 100644
--- a/champlain/champlain-map-source-factory.h
+++ b/champlain/champlain-map-source-factory.h
@@ -124,6 +124,10 @@ GSList *champlain_map_source_factory_get_registered (ChamplainMapSourceFactory *
  * CHAMPLAIN_MAP_SOURCE_OSM_AERIAL_MAP:
  *
  * Mapquest Open Aerial
+ *
+ * Deprecated: Mapquest isn't available any more and will be removed in the next release.
+ * As it doens't exist, it isn't registered to the factory and the 'create' method won't
+ * return any source.
  */
 #define CHAMPLAIN_MAP_SOURCE_OSM_AERIAL_MAP "osm-aerialmap"
 #endif