- actually enabled charset anchors in the engine (still not

used by the code generator)

- changed max repeat value in engine (to match earlier array fix)

- added experimental "which part matched?" mechanism to sre; see
  http://hem.passagen.se/eff/2000_07_01_bot-archive.htm#416954
  or python-dev for details.

Lib/sre_compile.py

@@ -208,7 +208,7 @@ def _compile(code, pattern, flags):
             else:
                 emit(OPCODES[op])
             emit(av-1)
-        elif op is MARK:
+        elif op in (MARK, INDEX):
             emit(OPCODES[op])
             emit(av)
         else: