Deprecate xformat and xsformat.

They were intended to be temporary, and now format and sformat use their
exact implementations and have for 6 months (though for some reason, xformat
and xsformat weren't turned into aliases when that happened, which I fixed
in this commit as well).
Undocument some deprecated functions.

They were marked for removal in the docs (many of them were intended to
be removed in January), so now they've been removed from the docs and
marked for removal from the code in November.
Removed some undocumented, deprecated functions from std.algorithm.

They were scheduled to be removed in January 2013 but weren't, so
they've been around as undocumented, and deprecated for a while now.
Merge pull request #1285 from jmdavis/deprecated

Move some deprecations along