osxfuse_requirement: add library and include paths

audit: allow deprecated options on new @ formulae.

As these may be migrations from another tap where we want to migrate
options across correctly.

In the installation whose prefix is other than /usr/local,
osxfuse library and include path must explicitly be specified during build.
Although brew's pkg-config is configured to prepend appropriates paths,
the prepended paths (/usr/local) supercede the original HOMEBREW_PREFIX.
This behavior will cause the linker to select libraries outside brew's tree.

By adding /usr/local to HOMEBREW_LIBRARY_PATHS, superenv ensures that appears
only after the HOMEBREW_PREFIX, and thus fixes this problem.

HOMEBREW_INCLUDE_PATHS is also configured like keg-only Formulae.

compat: deprecate Utils::JSON in favor of corelib JSON.

Load cask file in `.metadata` directory directly.

Cask: Add the choices option to pkg stanza

LLVM Clang fixes

We can filter it just for Clang and let it be used by anything else.

This was implemented before the rest of the file was refactored.

A more widely used style than relying on `if`/`else` returns.

This makes it easier to identify null versions when inspecting them.

audit: check formula name against blacklisted names.

Prefer brewed Clang over gcc-6 for needs :openmp

install: suppress redundunt warnings with `depends_on` requirement

Remove kernel extensions specified in `uninstall :kext`.

installer command accepts -applyChoiceChangesXML option to change
customize options on the GUI installer from the commandline.
(`man installer` for more detailed information)

The introduced option `choice` enables the choice changes to be supplied
via pkg stanza without tricks in preflight code.

When a formula depends on any requirements, they evaluated at most three times:
before locking, before installing dependent, before building formula.
When a non-fatal requirement is specified and thus evaluated three times,
mostly the same warning message is also emitted three times.

This change restricts printing the warning messages only when a bottle is
successfully installed or before building.
Since this timing is after the final dependency computation for each cases,
the warnings will be most useful to check what is not yet satisfied.

Fix flaky tests.

testbottest: don't use TEST_FIXTURE_DIR.

This isn't defined for formulae.

Clang has fully implemented OpenMP support as of LLVM 3.7, so if OpenMP
is required by a formula gcc is no longer the only choice of compiler.

Clang should be preferred over gcc because using gcc meant linking
against libstdc++, which is ABI incompatible with libc++. This may be
unnoticeable for some users, but it causes other builds to fail, e.g.
pstoedit when imagemagick was built with OpenMP. pstoedit is required
for the octave formula, so for some users this could be a significant
problem.

audit: don't check devel version_scheme/revision.

uninstall: ignore deprecations when uninstalling.

audit: check for HOMEBREW_PREFIX test path usage.

Handle `MethodDeprecatedError` because we want people to be able to
uninstall regardless of the content of their formula.

This is also not allowed.

As seen in https://github.com/Homebrew/homebrew-core/pull/6996.

bump-formula-pr: add --message option

utils/json: Replace OkJson with Ruby's core JSON.