Annotation tiles may become partially parsed just like regular tiles,
for example if a point annotation is added to the map before the style's
sprite has been loaded. In such cases, they need to be reparsed or the
annotation will not be rendered. Previously, the code path for reparsing
would be short-circuited by a dynamic_cast<VectorTileData*> followed by
a null check. This commit removes that case and adds (back) a virtual
reparse method to the TileData interface.
The callback will be called when any of the resources requested
from the network failed to load.
There is not recovery implemented yet, so the closest thing to
reseting the Map object and reloading all the resources would
be setting a new style.
Both Android and iOS now use pause/resume. The map thread is
always running, and be able to receive messages. When paused,
it will just refuse to render.
