…e VID/PID (libusb or hidapi or libftdi)

Added code for USBasp to check for bus:device match using the -P option. Syntax is -P usb:<bus>:<device> (same as current USBTiny implementation).

This also supports serial number check with the alternative -P usb:<serial_number> format (no ':').

In verbose mode, prints out bus/device/serial number for any found USBasps.

Only tested on Linux, but it works with HAVE_LIBUSB_1_0 on or off (there's some slightly different code in the two versions of usbOpenDevice()).

Change sense of check_for_port_argument_match() to return nonzero when there is a match.

Increase size of 'bus_num' and 'dev_addr' from 4 to 21.

Various cleanup, formatting changes, and simplifications.

Match trailing end of serial numbers.

Remove some unnecessary braces and parens.