Move tests on the highlight path until after the blacklist is checked so
that blacklisted paths are not tested. This should prevent hangs on dead
remote filesystems provided the path is blacklisted in
X_ZSH_HIGHLIGHT_DIRS_BLACKLIST.

Updated tests to 'default' highlight as the blacklist is now checked
before the path is tested.

Bug: https://github.com/zsh-users/zsh-syntax-highlighting/issues/528

The «=(<foo)» construct was highlighted in blue (globbing?) from the '>' to the ')'.

Closes #379.

Closes #472

Closes #497

See #497.

Fixes #474.

Adding «(e)» to the first subscript is a no-op: the subscript is known
to be safe due to the previous line.

No functional change.

This means --foo="bar" will have quotes highlighted.

This will set MATCH as needed for the next commit

Closes #481

This allows _highlight_arguments to put things in region_highlight prior
to the highlights decided by the helper functions, but decide on what
that prior highlight should be after the helpers have run.

Found-by: Matthew Martin

Closes #468.

Closes #277.

Closes #130

Closes #466.

Unbreaks build on pre-5.4.

This is a followup to the last commit, which was about issue #328.

These tests are taken from the original #328 pull request, with updated
expectations where applicable.

Review-by: Matthew Martin