Reimplemented fit to bounds

The new implementation is now public and takes advantage of MGLCoordinateBounds. It is re-ported from `Camera.prototype.fitBounds()` in mapbox/mapbox-gl-js to ensure correct behavior. A new function, MGLCoordinateBoundsMake(), makes it easier to create an MGLCoordinateBounds for use with this method.

include/mbgl/ios/MGLMapView.h

@@ -118,6 +118,14 @@ IB_DESIGNABLE
 *   @param animated Specify `YES` if you want the map view to animate scrolling and zooming to the new location or `NO` if you want the map to display the new location immediately. */
 - (void)setCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate zoomLevel:(double)zoomLevel animated:(BOOL)animated;
 
+/** Returns the coordinate bounds visible in the receiver’s viewport. */
+- (MGLCoordinateBounds)visibleCoordinateBounds;
+
+/** Changes the receiver’s viewport to fit the given coordinate bounds, optionally animating the change.
+*   @param bounds The bounds that the viewport will show in its entirety.
+*   @param animated Specify `YES` to animate the change by smoothly scrolling and zooming or `NO` to immediately display the given bounds. */
+- (void)setVisibleCoordinateBounds:(MGLCoordinateBounds)bounds animated:(BOOL)animated;
+
 /** The heading of the map (measured in degrees) relative to true north. 
 *
 *   The value `0` means that the top edge of the map view corresponds to true north. The value `90` means the top of the map is pointing due east. The value `180` means the top of the map points due south, and so on. */

include/mbgl/ios/MGLTypes.h

@@ -28,6 +28,13 @@ typedef struct {
     CLLocationCoordinate2D ne;
 } MGLCoordinateBounds;
 
+NS_INLINE MGLCoordinateBounds MGLCoordinateBoundsMake(CLLocationCoordinate2D sw, CLLocationCoordinate2D ne) {
+    MGLCoordinateBounds bounds;
+    bounds.sw = sw;
+    bounds.ne = ne;
+    return bounds;
+}
+
 NS_ASSUME_NONNULL_END
 
 #pragma clang diagnostic push

include/mbgl/map/map.hpp

@@ -95,6 +95,7 @@ public:
     void setZoom(double zoom, Duration = Duration::zero());
     double getZoom() const;
     void setLatLngZoom(LatLng latLng, double zoom, Duration = Duration::zero());
+    void fitBounds(LatLngBounds bounds, Duration = Duration::zero());
     void resetZoom();
     double getMinZoom() const;
     double getMaxZoom() const;