PyLong_AsLong in convert.pxd

[fchapoton]

see #169

not sure if this is correct. One could maybe remove the conversion ?

[tornaria]

The change is ok; cython 3.0 has a fallback in the form of

#define PyInt_AsLong                 PyLong_AsLong

and this will be removed in cython 3.1 afaict.

OTOH, I wonder if this PyInt_AS_GEN() function should be deprecated (and remove its use in cypari2/convert.pyx which seems to me dead code; I think isinstance(x, long) is equivalent to isinstance(x, int) in python 3).

It might be worthwhile to try building and testing with a trunk version of cython (what will be 3.1 I guess).

[tornaria]

As a matter of fact, the current implementation of PyInt_AS_GEN is "broken" in the sense that there is no error checking. Which should be fine for a python 2 int, but may break for a python 3 int. Using PyLong_AsLong does error checking so the new version is better.