fix compile of new cxx tests if tiff is not available - closes #2625

tests/cxx/tiff_io.cpp

@@ -1,8 +1,12 @@
+
+#if defined(HAVE_TIFF)
+
 #include "catch.hpp"
 
 #include <mapnik/image_reader.hpp>
 #include <mapnik/image_util.hpp>
 #include <mapnik/util/file_io.hpp>
+
 #include <mapnik/tiff_io.hpp>
 #include "../../src/tiff_reader.cpp"
 
@@ -273,4 +277,6 @@ SECTION("gray32f tiled") {
     TIFF_READ_ONE_PIXEL
 }
 
-}
+}
+
+#endif