PDP18B: Latest updates from Bob Supnik

- Added unix v0 terminal support
- Added 3-cycle databreak set/show entries
- Revised for dynamically allocated memory
- Added support for -u modifier (UC15 and Unix v0)

These changes are to support the Unix v0 bringup and to implement a
"Unix input" mode on the console terminal.  In Unix mode, CR and LF are
swapped (so that a modern terminal can use 'enter' instead of CTRK-J to
create the newline Unix expects), escape is mapped to altmode (175),
upper and lower case are enabled and the parity bit is forced to 1.  This
most closely matches the characteristics of the KSR-37, but there is no
definitive evidence of the terminal that was actually used.

PDP18B/pdp18b_lp.c

@@ -1,6 +1,6 @@
 /* pdp18b_lp.c: 18b PDP's line printer simulator
 
-   Copyright (c) 1993-2015, Robert M Supnik
+   Copyright (c) 1993-2016, Robert M Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -28,6 +28,8 @@
    lp09         (PDP-9,15) LP09 line printer
    lp15         (PDP-15)   LP15 line printer
 
+   10-Mar-16    RMS     Added 3-cycle databreak set/show entry
+   07-Mar-16    RMS     Revised for dynamically allocated memory
    13-Sep-15    RMS     Added APIVEC register
    19-Jan-07    RMS     Added UNIT_TEXT flag
    11-Jun-06    RMS     Made character translation table global scope
@@ -666,7 +668,6 @@ return detach_unit (uptr);
 /* LP15 line printer */
 
 #define LP15_BSIZE      132                             /* line size */
-#define LPT_WC          034                             /* word count */
 #define LPT_CA          035                             /* current addr */
 
 /* Status register */
@@ -681,7 +682,7 @@ return detach_unit (uptr);
 #define STA_EFLGS       (STA_ALM | STA_OVF | STA_IHT | STA_ILK)
 #define STA_CLR         0003777                         /* always clear */
 
-extern int32 M[];
+extern int32 *M;
 int32 lp15_sta = 0;
 int32 lp15_ie = 1;
 int32 lp15_stopioe = 0;
@@ -714,7 +715,6 @@ UNIT lp15_unit = {
 
 REG lp15_reg[] = {
     { ORDATA (STA, lp15_sta, 18) },
-    { ORDATA (CA, M[LPT_CA], 18) },
     { FLDATA (INT, int_hwre[API_LPT], INT_V_LPT) },
     { FLDATA (ENABLE, lp15_ie, 0) },
     { DRDATA (LCNT, lp15_lc, 9) },
@@ -730,6 +730,7 @@ REG lp15_reg[] = {
     };
 
 MTAB lp15_mod[] = {
+    { MTAB_XTD|MTAB_VDV|MTAB_NMO, LPT_CA, "CA", "CA", &set_3cyc_reg, &show_3cyc_reg, "CA" },
     { MTAB_XTD|MTAB_VDV, 0, "DEVNO", "DEVNO", &set_devno, &show_devno },
     { 0 }
     };