Added new scalar type

Added the new scalar type. This is different than direction since
direction relies on which way the mouse is pointing and scalar will
always be the same. Need to come up with a better name.
Added wall adding subroutines

Added subroutines to add walls to our nav array.
Position.c somehow got screwed up

Well I am working on an airplane, so I blame that and not my bad
coding.
Added new subroutines to print out walls

This will help with debugging the wall aspect of the nav array.
Anyway I hope to make this better in the future.
Added documentation to the code

Added some documentation to the code so that I know what I am doing
later down the road.
Renamed scalar to facing

Seems to be a better name than scalar. Facing simply means which way
something is facing to the mouse while the direction is saved for the
overall coordinate system. I might change this ...
Added a little bit more doc
Remove the postion alias

We shouldn't have to names for the position structure. So from now on
we are going to use pos_t instead of using struct position.
Renamed wall.* to nav.*

Just needed to rename the file names. All of the subroutines had already
been renamed but the files sticked around for a while.