* Use libusb to switch a PICkit4 or SNAP to AVR mode
* Fix case
* implement -xmode=pic
Thanks Wireshark
* Print PIC switch info messages
* Fix typo
* Rename SNAP and PICkit4 USB PID
* Make it possible to enter avr mode even when the tool is in bootloader/recovery mode
* Add -xmode to docs
* Tweak grammar
* Add -xmode support for pickit4_isp and snap_isp
still need to figure out how to actually trigger the mode switch form stk500v2.c
* Don't print "unable to open port" error on pgm->open softfail
* Add const
* Simplify SNAP/PICkit4 mode switching code
* Formatting
* Add extra argument to jtag3_open_common
This makes it possible to switch SNAP/PK4 modes from stk500v2.c as well, using pickit4_isp and snap_isp
* Improve extended parameter parsing
* Improve error message
* Improve extended parameter parsing
* Immediately exit after a mode switch
* Remove unnecessary line
* Add missing serial_close
* Remove unnecessary else
* Minor code tweaks
* Update docs
* Formatting
* Improve external parameter parsing and error handling
* Remove unused parameter
