Fixes #368.

Fixes a subset of issue #237.

This is related to a future "unbalanced { ( ) }" check for issue #344.

Also adds an XFail test for balanced braces for issue #344.

This was suggested on #355.

This manifested in completion of the form «./foo<TAB>» where there happened to
be a program called 'foo' in $PATH.

Fixes #354.
Closes #355.

This tracks the API change made in the previous commit, as suggested in the
(#if 0'd) deprecation warning.

This is a prerequisite for the next commit.

The incumbent code was wrong: the test of $in_redirection in the first hunk
would never have seen «(( in_redirection == 2 ))».  That had no visible
effect since options to sudo don't look like redirection operators.

The structure now mirrors the stall construct at the top of the loop.

Special handling for cursor imprint or partial path highlighting
is needed in more cases than accept-*. For example when accepting
a line from isearch, no accept-* widget is invoked.

The proper way is to use zle-line-finish.

Trumps #259.
Fixes #284.

The test passes so I'm adding it directly to master.

Just in case one of the interpolated variables contains a backslash.

Fixes #342.

If the separator feature is disabled, this makes it possible to
change the main 'path' styles in a running session without the
need to touch the '_pathseparator' styles, too.

Causes such expansions to be highlighted as [unknown-token] rather than as default (absent from $region_highlight).

Fixes #337.

Part of #337.

Fixes #231.
Fixes #330.

Assignments to positional parameters using scalar assignment syntax is
a feature: it is covered by upstream's test suite ("append to positional
parameter" in Test/A06assign.ztst).

This commit is based on the work done by
Jorge Israel Peña (blaenk) in #136.

Changes:
* Adjusted to changes on the latest master branch.
* Use regular path highlighter colors by default.
* Break out early if the separator color is the same to
  improve performance.
* Tests.

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.

The test being extended is highlighters/main/test-data/control-flow2.zsh.

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.

Inspired by #312.

Use correct indexing also for cursor-matchingbracket.

Fixup for 95d82568d8