Kill most warnings in lib/DtTerm.

Mostly missing headers, explicit parentheses and new prototypes.

Some Caveats:
* I haven't compile-tested the SVR4 getpty file, it might need another tweak
* There were operator precedence bugs in TermPrimCursor.c and TermPrimRender.c
  (^ vs. !=).  This might change behaviour, but at least I haven't experienced
  any crashes ...
* This adds a little more dependencies for include ordering, but unless we
  want to play the "headers that include headers that include headers..." game,
  this is unavoidable.

cde/lib/DtTerm/TermPrim/TermPrimDebug.h

@@ -58,5 +58,8 @@ extern unsigned char *debugLevel[256];
 #define	_TERM_DEBUG(c, a) \
 	_TERM_DEBUG_FLAG(c, 0, a)
 
+void _DtTermPrimDebugDumpEvent (FILE *f, Widget w, XEvent *ev);
+
+
 #endif	/* _Dt_TermPrimDebug_h */
 /* DON'T ADD ANYTHING AFTER THIS #endif... */