[phobos] User define datetime format

[Jose Armando Garcia]

Hi Jonathan et al.,

Is there any plan to add support for user define format string.
Windows, Linux and MacOS define the following function:

strftime - http://msdn.microsoft.com/en-us/library/fe06s4ak%28v=VS.100%29.aspx
            - http://linux.die.net/man/3/strftime
            - http://www.manpagez.com/man/3/strftime/

I would like to add support in std.log to customize the date and time
format in a log line and it would be great if this was supported by
std.datetime. Support for the inverse function strptime would be nice
too.

Thanks,
-Jose