ALL: Massive 'const' cleanup

These changes facilitate more robust parameter type checking and helps
to identify unexpected coding errors.

Most simulators can now also be compiled with a C++ compiler without
warnings.

Additionally, these changes have also been configured to facilitate easier
backporting of simulator and device simulation modules to run under the
simh v3.9+ SCP framework.

display/display.c

@@ -98,7 +98,7 @@ struct color {
 
 struct display {
     enum display_type type;
-    char *name;
+    const char *name;
     struct color *color0, *color1;
     short xpoints, ypoints;
 };