Fix export for ol.Geolocation.SUPPORTED
Fix export for ol.DeviceOrientation.SUPPORTED
Use @exportSymbol for exporting ol.webgl.SUPPORTED

For consistency with the way we export ol.DeviceOrientation.SUPPORTED and ol.Geolocation.SUPPORTED.
Merge pull request #1073 from elemoine/export-supported

Fix exports for ol.Geolocation | DeviceOrientation.SUPPORTED