Move the Tx callbacks on each to be trunk specific, not global so that we can set them per trunk.
Change prototypes for the Tx callbacks so that they pass a trunk specific private pointer to the Tx callbacks so that 921 and 931 can call each other directly.
change 921 so that it doesn't use a static array for it's trunk structure to match 931
use more enums.
more to come....

git-svn-id: http://svn.openzap.org/svn/openzap/trunk@96 a93c3328-9c30-0410-af19-c9cd2b2d52af