[Python-3000] Adding 'n' format presentation type to integers

[Eric Smith]

'n' is like 'g', but adds locale-specific thousands separators.

Issue 2802 (http://bugs.python.org/issue2802) points out that 'n' 
formatting isn't useful for integers, because it first converts to 
float.  There's no way to get 1,000,000 as a result, since 'g' converts 
to '1e+06'.

I propose adding 'n' as an integer format presentation type to PEP 3101. 
  The definition would be:

'n' - Number. This is the same as 'd', except that it uses the
               current locale setting to insert the appropriate
               number separator characters.

I already have the C code needed to implement this in Python/pystrtod.c 
(for floats), so it would just take some refactoring to get the integer 
formatter to use it.

If there is agreement, I'll update the PEP and implement this in 2.6 and 
3.0.

Eric.