Add manpage
Rework state management for audio calls

No need to try to keep local state, just use toxav_get_call_state().
We now can auto-accept calls by pre-attaching on the call_out FIFO.
Manpage update
Add -lrt to LDFLAGS
Fix build on kfreebsd
Check if the call id is valid before cancelling it
Update README
Update README
Update README
Update README
Update README
Check outfiles if they are still open

If not, abort receiving.
Fix file-transfers
Do a toxav_hangup() like we do elsewhere

This will trigger the callback and reset toxav internal states
accordingly.  In the callback we actually call cancelcall().
Don't close a random fd

if (f->rxstate == TRANSFER_INPROGRESS &&
    (fd = openat(f->dirfd, ffiles[FFILE_OUT].name, ffiles[FFILE_OUT].flags, 0666)) == -1 &&
    errno == ENXIO) {
    ...
} else {
    close(fd); <--- not always appropriate!
}
Style fix

Similar style as for detecting broken file transfers.
Fix request- and friend-management

When you got a request, but not accepted it via request/out/... and
instead sent a request yourself, it would not remove the FIFO.
This patch fixes this behaviour by iterating through the request-
list and removing the FIFO if it's still existing.
Additionally, actually make it possible to reject requests and
re-add your friends later by managing the internal tox-state
properly.
Use NSIG instead of _NSIG
Add nospam/ to manpage
Add kytv to LICENSE for contributing the manpage