PEP 342 implementation.  Per Guido's comments, the generator throw()
method still needs to support string exceptions, and allow None for the
third argument.  Documentation updates are needed, too.
diff --git a/Lib/symbol.py b/Lib/symbol.py
index eaf5a25..8219008 100755
--- a/Lib/symbol.py
+++ b/Lib/symbol.py
@@ -88,6 +88,7 @@
 gen_if = 331
 testlist1 = 332
 encoding_decl = 333
+yield_expr = 334
 #--end constants--
 
 sym_name = {}