[tz] proposed changes for Win32 and a improved mktime() algorithm

[Kees Dekker]

>Unfortunately the patch doesn't work well in boundary cases like overflow or 
>leap seconds, and (more generally) it is duplicating functionality that is 
>already present in tzcode. If the patch works for you in your situation that's 
>fine, but it's not generally suitable for tzcode.

Ok, no problem. Feel free to use its ideas, as the binary search is quite inefficient.
Overflow detection can be added, which will be done, if we have time.
I'm not sure whether leap second detection is absent. Anyhow, if you say on beforehand
that you are not interested in a fixed version, I don't spend much hurry to it.

Kees