Fix key repeats during VT switch.

Add keyc->postdown, which represents the key state as of the last mieqEnqueue
call, and use it when we need to know the posted state, instead of the
processed state (keyc->down).  Add small functions to getevents.c to query and
modify key state in postdown and use them all through, eliminating previously
broken uses.

include/inputstr.h

@@ -122,6 +122,7 @@ typedef struct _GrabRec {
 
 typedef struct _KeyClassRec {
     CARD8		down[DOWN_LENGTH];
+    CARD8		postdown[DOWN_LENGTH];
     KeyCode 		*modifierKeyMap;
     KeySymsRec		curKeySyms;
     int			modifierKeyCount[8];