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_rb.c

@@ -1,6 +1,6 @@
 /* pdp18b_rb.c: RB09 fixed head disk simulator
 
-   Copyright (c) 2003-2013, Robert M Supnik
+   Copyright (c) 2003-2016, 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"),
@@ -25,6 +25,7 @@
 
    rb           RB09 fixed head disk
 
+   07-Mar-16    RMS     Revised for dynamically allocated memory
    03-Sep-13    RMS     Added explicit void * cast
    14-Jan-04    RMS     Revised IO device call interface
    26-Oct-03    RMS     Cleaned up buffer copy code
@@ -77,7 +78,7 @@
 #define GET_POS(x)      ((int) fmod (sim_gtime () / ((double) (x)), \
                         ((double) (RB_NUMSC * RB_NUMWD))))
 
-extern int32 M[];
+extern int32 *M;
 extern int32 int_hwre[API_HLVL+1];
 extern UNIT cpu_unit;