bktr, gdb updtd

Joerg Sonnenberger has updated the bktr(4) driver to match what’s current in FreeBSD, including a new msp driver (from Linux), and support for the Terratec TValue, which was submitted by Patrick Mauritz.

cc3 has been switched back to stabs output, temporarily until DWARF2 support comes into gdb5 or DragonFly gets gdb6.