* Fix unused variable warnings
* Fix misleading indent warning
* Fix potential buffer overflow with fgets()
Was reading 256 bytes into a 255-byte array. The function would read at
most 255 bytes then try to append a nul (which would overflow), now will
read at most 254 bytes before appending the nul.
* Move isoCallback() from .h to .cpp file
Fixes warnings that the function is unused by every other file that
includes unixusbdriver.h.