Disambiguate abs() for gcc6

--- src/Geoscape/Globe.cpp	2014-06-13 21:14:43.000000000 +0200
+++ src/Geoscape/Globe.cpp	2016-10-03 16:35:38.988290974 +0200
@@ -1390,12 +1390,12 @@
 
 	if (fabs(sx)<0.01)
 	{
-		seg = abs( sy/(2*M_PI)*48 );
+		seg = abs((int)( sy/(2*M_PI)*48 ));
 		if (seg == 0) ++seg;
 	}
 	else
 	{
-		seg = abs( sx/(2*M_PI)*96 );
+		seg = abs((int)( sx/(2*M_PI)*96 ));
 		if (seg == 0) ++seg;
 	}