Add s64 type to common.h
Add Doppler to measurement struct, constrain mean carrier phase.

(Phase measurement work in progress)
Really correct solution time computation.
Apply satellite clock correction to TOTs and work around week rollover bug with current time handling.

The week rollover issue should still be fixed by properly determining the TOT week number rather than taking it from the ephemeris.
Remove mean constraint on pseudo ranges and phases, instead use reference channel.
Reduce matrix epsilon, was detecting valid matrices as singular.
Todo note in gpstime.
Keep track of nav bit phase.
Rejig navigation measurement struct.
Init min_TOT to maximum double