[ios] Move private geometry symbol visibility definitions to header

platform/darwin/src/MGLGeometry.mm

@@ -45,7 +45,6 @@ mbgl::LatLng MGLLatLngFromLocationCoordinate2D(CLLocationCoordinate2D coordinate
     }
 }
 
-MGL_EXPORT
 CLLocationDistance MGLAltitudeForZoomLevel(double zoomLevel, CGFloat pitch, CLLocationDegrees latitude, CGSize size) {
     CLLocationDistance metersPerPixel = mbgl::Projection::getMetersPerPixelAtLatitude(latitude, zoomLevel);
     CLLocationDistance metersTall = metersPerPixel * size.height;
@@ -53,7 +52,6 @@ CLLocationDistance MGLAltitudeForZoomLevel(double zoomLevel, CGFloat pitch, CLLo
     return altitude * std::sin(M_PI_2 - MGLRadiansFromDegrees(pitch)) / std::sin(M_PI_2);
 }
 
-MGL_EXPORT
 double MGLZoomLevelForAltitude(CLLocationDistance altitude, CGFloat pitch, CLLocationDegrees latitude, CGSize size) {
     CLLocationDistance eyeAltitude = altitude / std::sin(M_PI_2 - MGLRadiansFromDegrees(pitch)) * std::sin(M_PI_2);
     CLLocationDistance metersTall = eyeAltitude * 2 * std::tan(MGLRadiansFromDegrees(MGLAngularFieldOfView) / 2.);

platform/darwin/src/MGLGeometry_Private.h

@@ -99,7 +99,7 @@ NS_INLINE mbgl::EdgeInsets MGLEdgeInsetsFromNSEdgeInsets(NSEdgeInsets insets) {
     @param latitude The latitude of the point at the center of the viewport.
     @param size The size of the viewport.
     @return An altitude measured in meters. */
-CLLocationDistance MGLAltitudeForZoomLevel(double zoomLevel, CGFloat pitch, CLLocationDegrees latitude, CGSize size);
+MGL_EXPORT CLLocationDistance MGLAltitudeForZoomLevel(double zoomLevel, CGFloat pitch, CLLocationDegrees latitude, CGSize size);
 
 /** Converts a camera altitude to a map zoom level.
 
@@ -108,7 +108,7 @@ CLLocationDistance MGLAltitudeForZoomLevel(double zoomLevel, CGFloat pitch, CLLo
     @param latitude The latitude of the point at the center of the viewport.
     @param size The size of the viewport.
     @return A zero-based zoom level. */
-double MGLZoomLevelForAltitude(CLLocationDistance altitude, CGFloat pitch, CLLocationDegrees latitude, CGSize size);
+MGL_EXPORT double MGLZoomLevelForAltitude(CLLocationDistance altitude, CGFloat pitch, CLLocationDegrees latitude, CGSize size);
 
 /** Returns MGLRadianCoordinate2D, converted from CLLocationCoordinate2D. */
 NS_INLINE MGLRadianCoordinate2D MGLRadianCoordinateFromLocationCoordinate(CLLocationCoordinate2D locationCoordinate) {