dgburr

* Allow building with more recent SDKs * Export services so that they are accessible by external applications * Add optional callback mechanism so external applications can receive notifications via...

Also includes a few other fixes: 1. Move `PL` message into `NAV` class (sorry!) 2. Add `sigId` and `chn` fields to `RXM-SFRBX` 3. Rename `rtkStat` in `RXM-RAWX` to `trkStat`

Cipher objects are stateful, meaning that it is not possible to reuse the same object to decrypt multiple passwords. With the current implementation the first password will be decrypted successfully...

Per page 99 of https://www.u-blox.com/docs/UBX-21019746: byte 3 of the UBX-NAV-HPPOSLLH message contains a bitfield called `flags` which contains a single flag named `invalidLlh`