The longobject.diff patch looks fine, modulo some whitespace nits.  (Older 
C source files use width-8 tabs for indentation.)

Are you interested in adding documentation and tests (the latter in the 
test_capi module)?

One thing about the patch struck me as odd:  the use of nb_int means that 
PyLong_AsLongAndOverflow will happily accept floats, Decimal instances, 
etc.  Ideally, this would be nb_index instead, but I guess it has to stay 
nb_int for now, for consistency with PyLong_AsLong.  py3k also uses nb_int 
here and in various other PyLong_As*** functions;  I think these should be 
changed, but that's another issue.