Muddle 56 doesn't flush buffer on <CLOSE>

[atsampson]

@ZoBoRf found that Muddle 56's <CLOSE> doesn't flush its output buffer when closing a file - there's a detailed description and a test program in ZILCH-How-to.

I had a look at this, and it's because some of the IO code was updated for TOPS-20 but not for ITS. In particular, the ODSK and OTTY functions should set the C.DISK/C.TTY flags in -2(B) - the CLOSE code checks for those flags in the channel being closed and assumes it's a network channel if neither is set.

I've tried changing ODSK/OTTY to IOR in the appropriate flags after calling OPEN0/OPEN2. This gets into the right bit of code in BFCLOS but the .CALL SIOT it uses doesn't work - this either needs fixing, or replacing with a call to the usual code for writing bytes to a file (which is how Muddle 54 does it).

[atsampson]

.CALL SIOT only works on unit mode channels (says the comment in SYSTEM; ITS), and Muddle 54/56 both open files in block mode for "PRINT", so SIOT is not the right thing to use here.