Fix Muddle's CLOSE not flushing the output buffer.

There were two problems here:

- The FOPEN code in 56 uses new C.DISK/C.TTY flags to keep track of the
  channel type, so it knew what to do when closing the channel. The
  TOPS-20 open code had been modified to set these, but the ITS code
  hadn't, so CLOSE was assuming all channels were network channels.

  Fix: set those flags in ODSK and OTTY, as TOPS-20 does.

- The BFCDSK flush routine had been modified to use byte pointer writes
  to write the last incomplete word for both TOPS-20 (SOUT) and ITS
  (SIOT). But on ITS, SIOT only works in unit mode, and Muddle opens
  files in block mode.

  Fix: restore the working code from Muddle 54 for writing the last
  word. The only difference is that BFCDSK can now be invoked with the
  leftover byte count (C) being zero, so it needs to check at the
  start to avoid duplicating the last word in that case.

src/mudsys/fopen.36

@@ -896,6 +896,8 @@ IFN ITS,[
 ODSK:	MOVE	A,S.SNM(C)	; GET SNAME
 	.SUSET	[.SSNAM,,A]	; CLOBBER IT
 	PUSHJ	P,OPEN0		; DO REAL LIVE OPEN
+	MOVEI	0,C.DISK
+	IORM	0,-2(B)
 ]
 IFE ITS,[
 
@@ -1759,6 +1761,8 @@ TTYLP2:	MOVE	C,T.SPDL+1(TB)	; POINT TO P BASE
 	IORI	A,20		; THEN USE DISPLAY MODE
 	HRLM	A,S.DIR(C)	; STORE IN OPEN BLOCK
 	PUSHJ	P,OPEN2		; OPEN THE TTY
+	MOVEI	0,C.TTY
+	IORM	0,-2(B)
 	MOVE	A,S.DEV(C)	; GET DEVICE NAME
 	PUSHJ	P,6TOCHS	; TO A STRING
 	MOVE	D,T.CHAN+1(TB)	; POINT TO CHANNEL
@@ -4223,9 +4227,19 @@ IFE ITS,[
 	SUB	TP,[2,,2]
 ]
 IFN ITS,[
-	MOVE	D,[440700,,A]
-	DOTCAL	SIOT,[CHANNO(B),D,C]
-	 .LOSE	%LSFIL		;PRESUMABLY LOSSAGE MATTERS
+	JUMPE	C,BFCDF2	; NO CHARS LEFT TO WRITE?
+	PUSH	P,[-5]		; KLUDGE ADDED TO FILL LAST WORD WITH ^C
+	ADDM	C,(P)
+	MOVE	C,A		; FOR FUNNY AOBJN PTR
+	HLL	C,BUFSTR(B)	; POINT INTO WORD AFTER LAST CHAR
+	MOVEM	0,(A)
+	MOVEI	0,3		; CONTROL C
+BFCDF1:	IDPB	0,C
+	AOSE	(P)
+	JRST	BFCDF1
+	SUB	P,[1,,1]
+	PUSHJ	P,PGBIOO
+BFCDF2:
 ]
 	POP	P,C
 	JUMPN	C,BFCLSD