Updated version of my macros patch for PyLong type:
 - patch for Python trunk
 - define 3 macros: PyLong_SIGN(x), PyLong_EQUALS_ZERO(x), 
PyLong_NDIGITS(x)
 - just replace code by the equivalent macros

The goal is the make the code easier to read. It would also help if we 
change the PyLong implementation (eg. the 2^30 base patch).

My previous patch was for py3k, the new one is for Python trunk and is 
shorter. I only kept the most simple macros.