#9 switch multiplexor driver

[Mark Falco]

This patch adds support for the touch sensor
multiplexor specifically the swmux sold at
www.techno-stuff.com. Changing the ranges should make
it work with other similar passive multiplexors.

I'm not posting it as a patch file due to the ease of
integration.

copy swmux.h into legos/include
copy swmux.c into legos/kernel
add swmux.c to KSOURCES variable in
legos/Makefile.kernel
add the following to boot/config.h
#define CONF_DSENSOR_SWMUX //!< swmux sensor

recompile the kernel

I've deviated from the typical legos style of throwing
all sensor related code into dsensor.h This is just my
personal style, but I feel that dsensor is getting too
large. You can certainly paste the code in there if
you like.

I'm posting this for possible including in legos-0.2.7
so please send me any comments you have on it. Send
any comments to mfalco@onebox.com

[Mark Falco]