[niepce] Fix build failure on gcc 6

[Hubert Figuière <hub src gnome org>]

commit f676db787548f472685b8b9cf34b473dceb8f5dc
Author: Hubert Figuière <hub figuiere net>
Date:   Thu Apr 21 16:06:34 2016 -0400

    Fix build failure on gcc 6

 src/niepce/modules/map/mapmodule.cpp |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/niepce/modules/map/mapmodule.cpp b/src/niepce/modules/map/mapmodule.cpp
index 338a846..9ed8271 100644
--- a/src/niepce/modules/map/mapmodule.cpp
+++ b/src/niepce/modules/map/mapmodule.cpp
@@ -100,7 +100,7 @@ MapModule::on_lib_notification(const eng::LibNotification &ln)
                 }
             }
 
-            if (!isnan(latitude) && !isnan(longitude)) {
+            if (!std::isnan(latitude) && !std::isnan(longitude)) {
                 m_map->centerOn(latitude, longitude);
             }
         }