devattach function change

hi,

in order to use midi devices in read-only or write-only mode, i've made a
small change in the 'devattach' function. Now it takes a new "mode" argument
that must have one on the following values: 'ro', 'wo' or 'rw' respectively
for read-only, write-only and read-write modes.

So, if you upgrade to a new snapshot, don't forget to update your
/etc/midishrc and ~/.midishrc files. For instance the following lines:

	devattach 0 "/dev/rmidi4"
	devattach 1 "/dev/rmidi3"

have to be replaced by:

	devattach 0 "/dev/rmidi4" rw
	devattach 1 "/dev/rmidi3" rw

The goal of this change is to allow midish to use unix pipes as midi devices
(which are read-only or write-only). For instance, this allows scripts and
front-ends (or user programs) to pass midi messages to midish in real-time.
Furthermore, pipes can be used to sychronize multiple instances of midish
together....

cheers,

-- 
Alexandre