Auto merge of #404 - philippkeller:master, r=alexcrichton

add time, localtime

time, localtime and strftime are all in POSIX.1 and should IMO all be part of `libc`.

I [tested the bindings](https://github.com/philippkeller/apue-rust/blob/master/src/bin/f06-11-strftime.rs) - works fine on OSX and linux.

And: I added the netbsd aliases based on `time.h` of netbsd