PYLONG_BITS_IN_DIGIT is misconfigured on g++

[methane]

gcc and g++ interprets pyport.h in different way.

```
(system) inada-n@oldbench:~$ cat longbits.c
#include <Python.h>
#include <longintrepr.h>

int main() {
        printf("digit bits = %d\n", PYLONG_BITS_IN_DIGIT);
        printf("sizeof(digit) = %lu\n", sizeof(digit));
}
(system) inada-n@oldbench:~$ gcc longbits.c -I /usr/include/python2.7/
(system) inada-n@oldbench:~$ ./a.out
digit bits = 30
sizeof(digit) = 4
(system) inada-n@oldbench:~$ g++ longbits.c -I /usr/include/python2.7/
(system) inada-n@oldbench:~$ ./a.out
digit bits = 15
sizeof(digit) = 2
```

This breaks some extension modules. For example, see https://github.com/msgpack/msgpack-python/issues/169

Please backport this bugfix.
https://github.com/python/cpython/commit/050ba5ec1e941e05607ef29049bde08798387bcc

[Matthias Klose (doko)]

according to the upstream issue this is fixed since 2012.

[methane (songofacandy)]

@doko
Do you mean this is resolved in Ubuntu 12.04 LTS ?

Ubuntu 12.04 is used widely.
And this bug may break user data silently.
I really hope this bug is fixed in 12.04.