preparation for new 'is' operator; breaks bootstrapping again, sorry (use generated C code)

compiler/parser.nim

@@ -154,7 +154,7 @@ proc getPrecedence(tok: TToken): int =
     of '.': result = 5
     else: result = 1
   of tkDiv, tkMod, tkShl, tkShr: result = 8
-  of tkIn, tkNotIn, tkIs, tkIsNot, tkNot: result = 4
+  of tkIn, tkNotIn, tkIs, tkIsNot, tkNot, tkOf: result = 4
   of tkDotDot: result = 5
   of tkAnd: result = 3
   of tkOr, tkXor: result = 2