change way overloaded api functions are 'indexed'

[GoogleCodeExporter]

Right now, if there are two overloaded version of the same api function - ie,

doSomething(arg1)

and

doSomething(arg1, arg2)

...we store which one to use an an overload index; the issue with this is that 
the order that these overloaded methods are listed in is effectively random

Instead, should have a dict instead of a list, and index by a tuple of argtypes.

Original issue reported on code.google.com by elron...@gmail.com on 26 Jan 2011 at 1:55