~foura/midifs

start overhaul of midi parsing
nicer error message for unimplemented reads and writes
implement reads of the ctl file
implement raw reads and writes to the device.
more consistent error handling in mk.*dev
close unused ends of the pipe in pipeexec.
don't return if execl fails, instead abort
don't link libthread. this fixes -p meaning the fs is never served.
start implementation of 9p filesystem.
store channel info on the midi dev like cable
add license and readme
init. midi interface for pipes and usb devices is done.'

todo:
- the filesystem interface.
- write a manpage.