Description of Problem:

In xsane sources a number of preset area definitions is hardcoded
to 13 while an actual array of menu items is longer.  As a result
various menu entries important for North America vanish.

Attached is a patch which makes a compiler to compute that number
in lieu of a developer.  Curiously enough new recompiled binaries
do not have any effect until ~/.sane/xsane/xsane.rc is removed
(maybe clobbering of _some_ items is enough but this is not tested).