writeMap(): Adding ANGLE to directives saved

ANGLE is missing in the directives for the generated mapfile, when
calling mapfile.c:writeMap() ; this commit aims to save the custom
angle.

Author: pmauduit

mapfile.c

@@ -6002,6 +6002,7 @@ static void writeMap(FILE *stream, int indent, mapObj *map)
   colorObj c;
 
   writeBlockBegin(stream, indent, "MAP");
+  writeNumber(stream, indent, "ANGLE", 0, map->gt.rotation_angle);
   writeHashTableInline(stream, indent, "CONFIG", &(map->configoptions));
   writeString(stream, indent, "DATAPATTERN", NULL, map->datapattern); /* depricated */
   writeNumber(stream, indent, "DEBUG", 0, map->debug);