add unless stmt to pypy

unless.patch

diff -r c62cca56f289 pypy/interpreter/pyparser/pytokenizer.py
--- a/pypy/interpreter/pyparser/pytokenizer.py	Tue Dec 06 18:47:03 2011 +0900
+++ b/pypy/interpreter/pyparser/pytokenizer.py	Thu Dec 08 13:30:38 2011 +0900
@@ -169,7 +169,7 @@
                 if start == end:
                     raise TokenError("Unknown character", line,
                                      lnum, start + 1, token_list)
-
+                bpos = pos
                 pos = end
                 token, initial = line[start:end], line[start]
                 if initial in numchars or \
@@ -213,6 +213,11 @@
                         token_list.append(tok)
                         last_comment = ''
                 elif initial in namechars:                 # ordinary name
+                    if token == "unless":
+                        line = line[:start] + "if not" + line[start + 6:]
+                        pos = bpos
+                        continue
+                    
                     token_list.append((tokens.NAME, token, lnum, start, line))
                     last_comment = ''
                 elif initial == '\\':                      # continued stmt