Harmonize firmware function names
Remove useless max_upload_size check
Remove useless define from windows.c
Improve and add many error messages
Rename serial_set_baud_rate to serial_set_rate
Make teensy_detect OS-specific

HID report descriptors are reported very differently by
different OSes. Remove hid_get_report_descriptor and implement
teensy_detect for each OS.
Implement board detection on Windows (and fix compilation)