appletouch position calculation

[Florian Loitsch]

Two patches for the macbook touchpad (appletouch.c):

The first one avoids the interpolation when the number of fingers changes. 
This way user-space programs can filter the jumps that happen at that time.
A patch for the xorg synaptics driver that does exactly that can be found 
here:
http://florian.loitsch.com/touchpad/synaptics/

The second one implements different modes for calculating the position of the 
touchpad configurable through the x_position_mode and y_position_mode 
parameters. The default (0) is the average of all activated sensors (which 
is, what has been done before). The other modes (1, 2 or 3) take into account 
the position of each finger (resp. left-most/top finger, mean of all fingers 
or right-most/bottom finger).

I would appreciate any comments before sending them to the appletouch 
maintainer. (btw is the maintainer Dmitry Torokhov or Alessandro Rubini?)

The patches have been tested on 2.6.20.10 but apply fine on the official 
git-repository dc87c3985e9b442c60994308a96f887579addc39
and the linux-input git-repository 3f07d8796262f6aee135c8dd9a91210da9f888e4

mfg,
// florian loitsch