Memory card work: Show "CHECKING" when we've seen the card and

havn't finished checking it out yet (eg. write check).  This improves responsiveness:
a slow card will indicate that we see the card immediately, and it helps
diagnostics since we can easily tell if the machine sees a card.  Allow re-
establishing a memory card removed after finalization, as long as it has the
same serial number.

stepmania/src/GameConstantsAndTypes.cpp

@@ -122,8 +122,10 @@ XToThemedString( HoldNoteScore, NUM_HOLD_NOTE_SCORES );
 
 static const CString MemoryCardStateNames[NUM_MEMORY_CARD_STATES] = {
 	"ready",
+	"checking",
 	"late",
 	"error",
+	"removed",
 	"none",
 };
 XToString( MemoryCardState );