Changes the interface of _zsh_highlight_main_highlighter_check_path().

Suggested-by: m0viefreak

If possible, try to use the zsh/parameter module to get
information about a shell words.

This avoids subshells and is a huge speed improvement
on systems such as cygwin.

Note 1:
$commands does not know about PATH_DIRS. So in case
PATH_DIRS is set, 'type -w' is still used if nothing
else matches.

Note 2:
zsh/parameter can't distinguish between 'command' and
'hashed'. Adjusted the test for that case to XFAIL.

The ideal solution would be if whence had an option to
put the result in REPLY instead of printing it to stdout.

If possible, use zsh/parameter to avoid forks.

Fixes #263.

Found-by: m0viefreak
(in #298)

Consider indexing long buffers (say 300 chars). E.g. following line:
      integer offset=${${buf[start_pos+1,len]}[(i)$needle]}
will gradually go into large indices for first index [a,] and be kept
at large index for second index [,b]. Instead, we can remove already
processed characters from buf:
    proc_buf="${proc_buf[offset + $#arg + 1,-1]}"
$offset and $#arg are small, first index will not be large. $proc_buf
will be smaller and smaller and the second index [,-1] will run shorter
and shorter.

_zsh_highlight_add_highlight appends to region_highlight $1 $2 and the
next non-null parameter. If there is no non-null parameter, do nothing,
This is so that highlighters can add a style with fallbacks if the most
specific style is not defined. If none of the applicable styles are
defined, do the right thing and don't add an invalid entry to
region_highlight.

The pattern highlighter doesn't use this function as it'd need too large
of an API change.

zsh older than workers/28418 (zsh revision 23bdfc7fd2)
doesn't support the «${name:offset:length}» syntax.  Therefore, use the older
«$name[start,end]» syntax instead.

Followup to 3cb58fd7d7b9e42067ffcf24892114dc2c9b26e4, "Optimization: -1 is
extra computation of string length internally".

Fixes zsh-users/zsh-syntax-highlighting#279.

While here, also add a test for the '!' reserved word (which is highlighted
since c216242b).

This is a continuation of 451665cb2a which did
the same for the $PS3 prompt.

Reported-by: Sebastian Gniazdowski

./parse.zsh "zplugin.zsh" > out_norm.txt 106,17s user 7,84s system 98% cpu 1:55,85 total

./parse.zsh "zplugin.zsh" > out_opt.txt 51,91s user 7,44s system 99% cpu 59,912 total

% wc -l zplugin.zsh
3188 zplugin.zsh

The input to the $PS3 prompt is not commands, so the 'main' highlighter is
not applicable to it.

Fixes zsh-users/zsh-syntax-highlighting#268.

This fixes fd's specified by a (single) digit.  The named fd syntax remains an XFail.

The important part of this change is removing the second conjunct from the
condition; the remainder of the change gives one example of when that matters.

At this time, no user-visible consequences are known.

Fixes zsh-users/zsh-syntax-highlighting#101.

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

Followup to 0d1bfbcbfa.

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 ";".

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.