Updated turtle API

The updated turtle API.
Fixing (to an extent) a deficiency in current native API implementation.
Allows automatic calibration and arbitrary course setting, rotation using specific angle, and keeps internal track of position and course changes.

Changes to existing methods:
Internal changes to all movement methods for course/location tracking.

New properties:
turtle.directions[indent=1]a dictionary table to translate numeric directions into verbal form. State-dependent.[/indent]

turtle.location() read-only[indent=1]Returns current turtle location, in order: x, y, z as returned by GPS API, bearing (0-3 clockwise, 0 being East/Forward), inertial navigation flag (true if using inertial navigation).
Usage example:

local x, y, z, b, i = turtle.location()
io.write("Unit " .. (os.getComputerLabel() or os.getComputerID()) ..
  " at (" .. x .. "," .. y .. "), altitude " .. z ..
  ", facing " .. turtle.directions[b])
if i then
  print(", using inertial navigation.")
else
  print(".")
end

[/indent]

turtle.version() read-only[indent=1]Returns API internal version.[/indent]

New methods:

turtle:calibrate( boolean verbose )[indent=1]Attempts a short calibration sequence and return turtle to the starting position. Working GPS network and an opened modem on turtle is required in order for it to work.
verbose - allows printing of progress information.
Returns true, if calibration was successful, othervise false.
Note the ":" - this function call is required to be self-referenced.[/indent]

turtle.rotate( int angle )[indent=1]Performs a rotation arbitrary number of times into given direction. Negative number will cause turtle to rotate counter-clockwise.
Due to turtle being heavily armoured and overall aimed to achieve a result rather performing a process, only necessary amount of maneuvering will be executed at a time.[/indent]

turtle.setCourse( int course )[indent=1]Attempt to point a turtle into specific direction (0-3 clockwise, with 0 being East/Forward)
Negative course allowed.
Returns true if succesful, or false othervise.[/indent]

Installation
Dump archive contents into minecraft/mods folder.

Reports and suggestions are welcome.

UPD 20120504-1: Sneaky edit
+ Added version properly. You can check for correct API installation by addressing turtle.version(). If it works, then you have it all proper. If not, you probably screwed something.

UPD 20120504:
+ Full inertial navigation.
* Rewritten and better state reporting.

UPD 20120424:
! Finally made it's way to my Subversion repo. No more code loss due to power outages.
* Fixed directions tables.
* A few preparations for inertial navigation.

UPD 20120423:
* More stupid error fixes.
* More consistency fixes.

UPD 20120422:
* Fixed some stupid errors in course handling.
* Split native call in two parts for easier code reuse.

Ok, update pending. In it: Full inertial navigation support, no longer in need for permanent GPS pestering.
Boot-up state considered to be the (0,0,0,0), until contacted with GPS network.
Coordinates are stored once and tracked onward through stateful navigation sequence.
The code is fully functional, just needs a cleanup and final proof-reading.

Found one issue, which I'm not sure how to classify.
To make this API run straight, you need to init your GPS beacons with (X, Z, Y) coords (so that altitude is last, as it should).