Fixes zsh-users/zsh-syntax-highlighting#109.

Similar to 59fbdda64c in the 'main' highlighter.

This builds upon the test harness auto-cleaned-up directories work (c01533920).

There's simply no reason to use such names, now that the filename is no longer
itself test data.

Fixes zsh-users/zsh-syntax-highlighting#182.
Prerequisite for testing issue #228.

* tests/test-highlighting.zsh
  (run_test): Move functionality to run_test_internal; make run_test be a wrapper
    that handles creating and cleaning up the tempdir.

* tests/README.md: Document the new feature.

* "highlighters/main/test-data/path-space- .zsh"
* highlighters/main/test-data/path-tilde-named.zsh
* highlighters/main/test-data/path.zsh
    Change test data to not depend on being run from the source directory.

Followup to c0dafd1d850e582291b41d693369794d1ea31343, which changed the highlight of
those ')'s from <nothing> to [reserved-word].

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.)