Finally, a working parser!

--> At least, it parses the sample file correctly

- I reverted the choice of using a skip parser, because it was failing and I couldn't figure out why. This means there's a lot of *ws where whitespace can go.
- Grammar rearranged a little

rsrc/boes/town/t0.spec

@@ -1,6 +1,8 @@
 
 # Sample special node sequence.
 
+def Varn = 3
+
 @if-gold            # The first node is node 0
     ex1  50, 5      # If they have 50 gold, take it and jump to node 5
     goto 1          # Otherwise, jump to node 1
@@ -8,4 +10,4 @@
     msg  2          # Shows string 2; the omitted argument is assumed to be -1
 @town-visible = 5   # Explicitly specify node number
     msg  3,4        # Shows strings 3 and 4 in the message dialog
-    ex1  3,1        # Town 3, set visibility to true
+    ex1  Varn,1     # Town 3, set visibility to true