[core] Fix build when building Qt Location plugin for Android

- log2 is not available on Android before API 18.
- Android doesn't have 'round' on the std:: namespace when using g++.

Co-authored-by: Thiago Marcos P. Santos <thiago@mapbox.com>

src/mbgl/util/tile_cover.cpp

@@ -4,6 +4,7 @@
 #include <mbgl/map/transform_state.hpp>
 #include <mbgl/util/tile_cover_impl.hpp>
 #include <mbgl/util/tile_coordinate.hpp>
+#include <mbgl/math/log2.hpp>
 
 #include <functional>
 #include <list>