[Cython] long literal integers

[Robert Bradshaw]

Currently there is no way to output literal C long, long long values,  
or unsigned long values. Also, large integer values used in a python  
context are truncated. It does, however, parse a trailing L to create  
a Python long.

I propose that we update this to pass the trailing L (and LL) to the  
underlying C code, as well as accepting the unsigned suffix (also  
passed to C the code), and covert large integer literals into Python  
longs without truncating. This is slightly backwards incompatible, so  
I wanted to get people's feelings on this before making the change.

- Robert