Fix broken ddoc build for std/regex/package.d.
Update std.range.* docs.

The previous docs were simply dissected from the original std.range docs, and
the text in each module is truncated and awkward to read. The main package.d
docs were also missing links to the submodules. So, update the docs to reflect
the current state of things.
Fix broken PHOBOSSRC link.

This is caused by Ddoc's "helpful" auto-highlighting of every occurrence of the
name of the module, including places where it's not very helpful.
allow casting Typedef to another Typedef
Fix issue 12589 - std.random.randomCover fails for empty ranges
Remove redundant initialization
Update std.container docs to reflect new submodules.

Improve wording in std.container docs.
Boilerplate docs for std.container.*.

Improve std.container.* documentation.
Merge pull request #2787 from sinkuu/randomcover

Fix issue 12589 - std.random.randomCover fails for empty ranges
Merge pull request #2788 from quickfur/std_container_docs

Update std.container.* docs to reflect submodules
Merge pull request #2776 from IgorStepanov/Typedef-opCast

allow casting Typedef to another Typedef
Merge pull request #2771 from quickfur/issue13766

Issue 13766: Fix broken ddoc build for std/regex/package.d.