Move Cask fixtures to `test/support/fixtures`.

language_module_requirement: use arrays.

This is cleaner, easier to understand how the arguments are split and
fixes #1799.

man: remove an unnecessary `else`

Add docs on persisting settings across upgrades

caveats: tweak keg-only messaging.

Slim down the existing text and make it more obvious what's happening.
Note specifically how to add it to your PATH to convince people to try
that instead of `brew link --force`.

Remove some remnants of Ruby 1.8.7 support

xcode: reduce minimum CLT version.

This should be 1.0.0 to be nicer to 10.7 users.

Fixes #1893.

audit: exempt wine's deps from the universal deprecation

`odie` causes the process to exit immediately, so there's no need for the
`regenerate_man_pages` call to be conditional.

Since this hack is no longer required, and `Emoji.tick` and `.cross` are
only called in one place, I think it's better to just inline them there
rather than having methods on `Emoji` that just return a one-character
String.

tests: automatically restore ENV in teardown

Fix installer deleting artifacts if they already exist.

Add internal command to calculate appcast checkpoint.

Cask: cleanups internal stanzas

This was deprecated and had all formulae removed in:
https://github.com/Homebrew/homebrew-gui/pull/52

Remove legacy cask cache instead of migrating.

Suggested by @reitermarkus in
https://github.com/Homebrew/brew/pull/1890#discussion_r97234536, and
then I added the \A and \Z.

bottle: fix regex