ENH: cpython.time to expose stdlib time.localtime etc

There is a libc.time available from which I think I can patch together something equivalent to https://github.com/python/cpython/blob/master/Modules/timemodule.c#L490, but itd be nice to have a canonical version exposed directly.

[scoder]

Yeah, apparently, it’s a GNU specific extension. The usual way we deal with those is to add them to the struct if it’s reasonable, because it doesn’t normally hurt to let Cython think they are there as long as users don’t write time into their code. But struct-dict conversion makes this … annoying.

In this case, I would remove the fields. We can add them in some other .pxd file if someone wants them. Does that sound reasonable?

[da-woods]

There isn’t currently a mechanism to say “copy this field only if it exists on this platform”.

It would be possible to implement this mechanism in the struct-to-dict converter functions in C++11. I’m not really convinced it’s a good idea to have the behaviour vary so much depending on the compiler, but it could be done if there was a real use for it.