main: Probe dirs after blacklist

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

zsh/macOS bug: http://www.zsh.org/cgi-bin/mla/redirect?WORKERNUMBER=42891

docs: Fix typos

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.

Fixes #480.

The new failure mode is:
.
    Running test main
    Bail out! On './highlighters/main/test-data/glob.zsh': Either 'PREBUFFER' or 'BUFFER' must be declared and non-blank
    Bail out! On './highlighters/main/test-data/glob.zsh': output on stderr
    Running test pattern

Fixes #478.

Found-by: Matthew Martin

Closes #468.