simulators with global variables PC, SP and BC: Avoid name space collisions.

Avoid potential name space collision for the global variables PC, SP and BC
when readline is dynamically loaded.  For some unknown reason, ncurses
exports these internal variables which may be needed in the context of
how ncurses is used by readline implementations.  In any case, these
variable names are common in simulators, so there is an undesired
interaction between simulator internal variables and the simplest
solution is to rename these simulator global variables where they exist.
Another alternative is to merely declare these variables static when
they happen to only be referenced in a single simulator source module.

PDP10/kx10_defs.h

@@ -30,6 +30,9 @@
 
 #include "sim_defs.h"                                   /* simulator defns */
 
+/* Rename of global PC variable to avoid namespace conflicts on some platforms */
+#define PC PC_Global
+ 
 #if defined(USE_ADDR64)
 #error "PDP-10 does not support 64b addresses!"
 #endif