[phobos] Deprecation of std.date

[Jonathan M Davis]

I've been going through the process of making Phobos use std.datetime instead of 
std.date. It isn't all that many changes, but it does mean that we're going to 
need to deprececate several functions outside of std.date and std.dateparse (all 
in std.file IIRC) and of course the modules std.gregorian, std.date, and 
std.dateparse. That's fine. The problem, however, is marking them as "scheduled 
for deprecation" with a pragma rather than just marking them as deprecated. It 
works just fine to mark them as scheduled for deprecation with a pragma, but it 
means that the output for the unittest build of Phobos spits out

std.date has been scheduled for deprecation. Please use std.datetime instead.
std.dateparse has been scheduled for deprecation. Please use std.datetime 
instead.

almost every other line (as opposed to std.gregorian, which prints out its 
message once or twice). It's definitely annoying, albeit temporary.

Is it acceptable to pollute the output for the build that thoroughly, or should 
I should I just mark the std.date-related stuff as deprecated instead of 
scheduled to be deprecated, or are we willing to have the build output flooded 
with "scheduled for deprecation" messages for a release or two?

- Jonathan M Davis