[tz] include implementations of str{f,p}time{,_l} in tzcode

[Paul_Koning at dell.com]

> On Oct 30, 2015, at 9:54 AM, Christos Zoulas <christos at zoulas.com> wrote:
> 
> 
> Hello,
> 
> I think that it is an omission for those functions not to be included
> in tzcode. They are tightly bound to the rest of the time code
> implementation and although standardized, the implementations that
> the most popular operating systems provide vary in behavior.
> 
> Yes, I understand that there are portability considerations (locale
> for example) that need to be handled, but not including them is taking
> the easy way out.

If tzcode needs to supply its own versions because the OS supplied versions aren't sufficient or consistent enough, it might make sense to give them different names.  Otherwise things get very confusing.

It might also be useful to report those inconsistencies to the OS's that have them, as bugs to be fixed.

	paul