the JTAGICE3 programmer handle a list of PIDs, by trying each of them
in sequence. Use a single, central jtag3_open_common() function to
handle the common code of all jtag3_open_* functions. Centralize all
USB VID/PID definitions in usbdevs.h.
git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@1283 81a1dc3b-b13d-400b-aceb-764788c761c2