Followup to 0d1bfbcbfa.

Reported-by: Antony Lee

The following warnings are issued by zsh as of zsh-workers/37018 (commit
de9effbce601 to zsh itself):

_zsh_highlight_main_highlighter_highlight_dollar_string:17: array parameter match created globally in function _zsh_highlight_main_highlighter_highlight_dollar_string
_zsh_highlight_main_highlighter_highlight_dollar_string:17: array parameter mbegin created globally in function _zsh_highlight_main_highlighter_highlight_dollar_string
_zsh_highlight_main_highlighter_highlight_dollar_string:17: array parameter mend created globally in function _zsh_highlight_main_highlighter_highlight_dollar_string
_zsh_highlight_main_highlighter_highlight_dollar_string:17: numeric parameter parameter MBEGIN created globally in function _zsh_highlight_main_highlighter_highlight_dollar_string
_zsh_highlight_main_highlighter_highlight_dollar_string:17: numeric parameter parameter MEND created globally in function _zsh_highlight_main_highlighter_highlight_dollar_string
_zsh_highlight_main_highlighter_highlight_dollar_string:17: scalar parameter MATCH created globally in function _zsh_highlight_main_highlighter_highlight_dollar_string
_zsh_highlight_main_highlighter_highlight_string:11: array parameter match created globally in function _zsh_highlight_main_highlighter_highlight_string
_zsh_highlight_main_highlighter_highlight_string:11: array parameter mbegin created globally in function _zsh_highlight_main_highlighter_highlight_string
_zsh_highlight_main_highlighter_highlight_string:11: array parameter mend created globally in function _zsh_highlight_main_highlighter_highlight_string
_zsh_highlight_main_highlighter_highlight_string:11: numeric parameter parameter MBEGIN created globally in function _zsh_highlight_main_highlighter_highlight_string
_zsh_highlight_main_highlighter_highlight_string:11: numeric parameter parameter MEND created globally in function _zsh_highlight_main_highlighter_highlight_string
_zsh_highlight_main_highlighter_highlight_string:11: scalar parameter MATCH created globally in function _zsh_highlight_main_highlighter_highlight_string

zsh prior to workers/32609 (commit 9d47e8398d)
does not support the (-n)-less «[[ $var ]]» syntax.

Fixes zsh-users/zsh-syntax-highlighting#225.

This is already done for commands prematurely terminated by ";".

These tests are based on the patches contributed in those issues:

    commit 9d9df4fe80 (upstream/pr/167)
    Author:     Miciah Masters <miciah.masters@gmail.com>
    AuthorDate: Thu Apr 23 20:28:24 2015 -0400
    Commit:     Miciah Dashiel Butler Masters <mmasters@redhat.com>
    CommitDate: Thu Apr 23 20:28:24 2015 -0400

        Highlight comments

    M       highlighters/main/main-highlighter.zsh
    A       highlighters/main/test-data/comments.zsh

    commit d94f1a037f (upstream/pr/163)
    Author:     sonnym <michaud.sonny@gmail.com>
    AuthorDate: Fri Mar 6 18:27:57 2015 -0500
    Commit:     sonnym <michaud.sonny@gmail.com>
    CommitDate: Fri Mar 6 21:16:27 2015 -0500

        highlight comments when interactive_comments is on

    M       highlighters/main/main-highlighter.zsh
    A       highlighters/main/test-data/comment-embedded.zsh
    A       highlighters/main/test-data/comment-leading.zsh

Patch-by: sonnym <michaud.sonny@gmail.com>
Patch-by: Miciah Masters <miciah.masters@gmail.com>
(corrected and refreshed for harness changes by me)

This causes the ':start:' state to be set in $next_word in iteration N-1,
rather than to only be added to $this_word in iteration N.

The word following 'sudo' was considered :regular:, although it isn't.

Fixes zsh-users/zsh-syntax-highlighting#166.
Fixes zsh-users/zsh-syntax-highlighting#194.
Builds upon the issue #207 work.

The change of behaviour is triggered by test-data/sudo-redirection.zsh: the iteration
on "otheruser" sets $next_word to ":regular::sudo_opt::start::sudo_opt::start:" before
this patch, but to ":regular::sudo_opt::start:" after it (note the deduplication).

The fix for issue #9 was accidentally broken by the penultimate commit.

Note that we don't care about aliases to ZSH_HIGHLIGHT_TOKENS_COMMANDSEPARATOR
entries, since the code deals with aliases at command position.

Use this to remove [path_prefix] highlighting during accept-* widgets.
This causes ": file.tx<CR>" to remove the underline from "file.tx", like
": file.tx<SPACE>" already does.  (Assume 'file.txt' exists.)

It's the widget's caller's responsibility, not ours, to add '--' where due.  If
we do it, two instances of '--' might result.  (I haven't been able to provoke
this problem.)

If this commit causes problems, the cause would be widget-callers that don't
pass '--' although they should.

test failure would not be reflected by the exit code of 'make'.

Setting a shell parameter in the left-hand side of a pipe is not visible to
commands after the pipe, because the left-hand side forks.  (That's true both
in 'sh' used by 'make' and in 'zsh' that runs tests/test-highlighting.zsh, at
least on my system.)  Therefore, move the colorizing hook to where it doesn't
interfere with setting the $something_failed (in tests/test-highlighting.zsh)
and $result (in Makefile) parameters.

Fixes zsh-users/zsh-syntax-highlighting#187.
Adds a test for zsh-users/zsh-syntax-highlighting#204.

Color is only added when "make test"'s stdout is a tty.