When running python2.5 under valgrind and running
    exec ""
valgrind issues the following warning:

==6661== Conditional jump or move depends on
uninitialised value(s)
==6661==    at 0x403EAF3: parsetok (parsetok.c:189)
==6661==    by 0x40ED673: PyParser_ASTFromString
(pythonrun.c:1354)
==6661==    by 0x40EF852: PyRun_StringFlags
(pythonrun.c:1225)
==6661==    by 0x40CB7FF: PyEval_EvalFrameEx (ceval.c:4202)
==6661==    by 0x40CC8E5: PyEval_EvalCodeEx (ceval.c:2833)
==6661==    by 0x40CCA74: PyEval_EvalCode (ceval.c:494)
==6661==    by 0x40EF3A1: PyRun_InteractiveOneFlags
(pythonrun.c:1264)
==6661==    by 0x40EF5A2: PyRun_InteractiveLoopFlags
(pythonrun.c:714)
==6661==    by 0x40EF6CA: PyRun_AnyFileExFlags
(pythonrun.c:683)
==6661==    by 0x40F930D: Py_Main (main.c:496)
==6661==    by 0x8048591: main (in /usr/bin/python2.5)

Valgrind does not give warnings when doing the same
thing with python2.4.3.

After further investigation, it looks like
tok->line_start is uninitialized.  Initializing to null
in tok_new() removes the valgrind warning, but I have
no idea if this is the correct fix.