Fixed issue #1382

- Ashtech driver is no longer checking fix status from comparing
  coordinates to 0.0;0.0;0.0, instead it's checking fix type in GGA or
  checking coordinate exsistance in POS. This removes compiler warning
  about float euqality comparison.

- Fixed compiler warning about comparison between signed and unsigned
  int

- Fixed compiler warning about class property masking
maybe check for `<= 0` as you never know if something goes wrong before this line especially if someone adds more code in the future for example.