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/TermPrimScroll.c

@@ -514,11 +514,11 @@ _DtTermPrimScrollText(Widget w, short lines)
     if (0 == lines)
 	return;
 
-    if (tw->term.jumpScroll &&
+    if ((tw->term.jumpScroll &&
 	    ((lines + tpd->scroll.jump.scrollLines) >
 	    (tw->term.rows -
 		tpd->scrollLockTopRow -
-		(tw->term.rows - 1 - tpd->scrollLockBottomRow))) ||
+		(tw->term.rows - 1 - tpd->scrollLockBottomRow)))) ||
 	    ((lines + tpd->scroll.jump.scrollLines) <
 	    -(tw->term.rows -
 		tpd->scrollLockTopRow -