[tz] source code changes in tzcode2013d: int_:fast32_t

[Alois Treindl]

I noticed that a lot of source code changes were done in tzcode, for 
example many variables which were of type long have been changed
to int_fast32_t.

On my system, a x86_64 Linux, we get: typedef long int_fast32_t.
So as expected, it comes out the same. long is 64 bit.

But I wonder about the rationale behind the naming of this type: is it 
supposed to hold only 32-bit values? If it is supposed not to suffer 
from 32-bit overflow problems, i.e. meant to be wider than 32 bits, why 
is it named the way it is named?

A general question: there is very little documentation for the source 
code in general. Would it not be appropriate for the maintainers of the 
code to include more internal documentation?