Minor additions to support node mobility events:

	* lib/libtb/tbdefs.h, lib/libtb/tbdefs.c, sql/database-fill.sql:
	Add SETDEST as an event type and NODE as an object type.

	* tbsetup/ns2ir/node.tcl:
	Add location (X_, Y_, Z_) and orientation attributes for mobile
	nodes.

	* tbsetup/ns2ir/sim.tcl:
	Add a "setdest" event for node types that lets the user move a
	mobile node.