NMEA/Derived: move code from ResetFlight() to many Clear() methods

Each struct should be responsible for its own values.
InputEventsActions: eliminate duplicate ToAircraftState() call
NMEA/Info: move ToAircraftState() to Aircraft.cpp

Prepare to make it independent of NMEA_INFO.
GlideComputerAirData: add local reference variables

Code simplification.
NMEA/Info: move AltitudeAGL to TERRAIN_ALT_INFO

AltitudeAGL is a calculated value, it does not come from the GPS.
This change requires ToAircraftState() to get a DERIVED_INFO
reference.

More calculated attributes will follow.
NMEA/Info: move working_band_* to struct ThermalBandInfo

These are calculated values.
WayPointFile: Removed trivial function add_waypoint()

add_waypoint() gets a waypoint instance that isn't used anymore in all occurences.
we can simply pass that to append() because that function will create an internal copy anyway.
WayPointFile: Removed compressed check from Save()

The Save() function for the compressed WayPointFile isn't called ever and
a WayPointFile shouldn't know anything about compression anyway.
WayPointFile: Added terrain class member and SetTerrain() function

This reduces the endless parameter passing of the terrain pointer
WayPointFile: Removed compressed class member

The value is only relevant for parsing to determine the right LineReader.
In WayPointGlue::ReadWaypoints() we know whether it should be compressed
or not without extra ZipFile opening operations.
WayPointFile: Removed trivial static function AltitudeFromTerrain()
dlgWaypointEdit: Removed outdated compiler bug hack

- RasterTerrain.h doesn't exist anymore
- RasterTerrain.hpp is now included anyway
README: additional Linux+Android build dependencies
NMEA/InputLine: fix potential assertion failure at end of line

By assigning an empty string literal to "data", the assertion "endptr
<= end" may fail on the next call, because the string literal may
point to a location after "end".  Better assign "data=end", because
that is guaranteed to point to the end of the line.
NMEA/InputLine: return default value when column is empty

Check data==end, and set the default value when both are equal,
i.e. nothing has been parsed.
RoutePlanner: methods to return copy of RoutePolars
GlideComputerTask/RoutePolars: update polar always

The RoutePolars structure will be used for fast terrain intersection
lookup elsewhere (waypoints display), so even if a task isn't defined,
we should update the RoutePolars structure.
ProtectedTaskManager/GlideComputer: refactoring for RoutePlanner reuse

AirspaceRoute is relocated to ProtectedTaskManager so the route planner structures,
particularly the RoutePolars instance can be re-used in other threads.
This will be used to check terrain intersections for waypoint display,
and ultimately for filtering of abort mode alternates.

This will contribute to resolution of #736.
AbortTask: use RoutePolars objects.

These will be used for fast terrain lookups.
RoutePolar: default cruise alt where not required