Plane: change threshold for no glide slope to 20m

40m is quite high for most planes
Plane: remved int cast

not portable
Plane: use bitfields in auto_state
Plane: prevent cross-track on some WP types

when finishing a takeoff or when a user forces a WP change don't do
any cross-tracking. This avoids a problem where the plane tries to
line up with a track completely unrelated to the track currently being
flown
AC_Motors: make get_throttle_out const
AC_PosControl: smooth take-off with accel PID's I term

This avoids an instantaneous jump in throttle during take-off by loading
the accel PID's I term with the expected change in throttle level
Copter: minor formatting fix
AP_RangeFinder: Added a call to sonar.update in RFIND_test
AC_PosControl: remove 20cm on takeoff
Copter: Add takeoff enum for guided_mode
Copter: Handle MAV_CMD_NAV_TAKEOFF command to takeoff in guided mode only
Copter: Add guided_takeoff_start and guided_takeoff_run functions
Copter: increase RATE IMAX param desc ranges

Also remove unused STB_RLL_I and STB_RLL_IMAX descriptions because these
parameters no longer exist
AP_Terrain: added extrapolation based on last available data

if we run out of terrain data then extrapolate using the last
available terrain height at the AHRS position. This can be used to
cope with GCS outages over long distances where the terrain data isn't
preloaded
Plane: use terrain extrapolation

use best effort extrapolation if we run out of terrain data
AP_TECS: added TECS_PITCH_MAX and TECS_PITCH_MIN

this allows the TECS controlled pitch limits to be smaller than the
FBWA limits. It is common for a human pilot to want a bit more
discretion over pitch than you want the automatic controller to use
Plane: make STAB_PITCH_DOWN in degrees

try to avoid new centi-degrees parameters
DataFlash: added TERR log message for terrain data
AP_Terrain: added dataflash logging
Plane: use dataflash logging for terrain