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.

Found-by: Matthew Martin

Closes #468.

Closes #277.

Closes #130

Closes #466.

This is a followup to the last commit, which was about issue #328.

These tests are taken from the original #328 pull request, with updated
expectations where applicable.

Review-by: Matthew Martin

Fixes highlighting of `ls \~`. Closes #328.

Travis (as currently configured) is one such platform.

No test because _zsh_highlight_main__type() falls back to 'type -w' which runs
'rehash' implicitly, so on systems where 'sudo' is installed it's not possible
to simulate its being absent.

Test by forcing _zsh_highlight_main__type() to return 'none' when the
argument is [[ $1 == 'sudo' ]], and: (1) Run 'make test' and confirm
that all tests either pass, or fail and the first test point that fails
is one that expects "sudo" at command position to be highlighted as
'command'; (2) In an interactive zsh, 'sudo' at command position is
highlighted as an error.

Unbreak build for 5.0.8 and earlier.

Closes #382.

The functions can remain defined because, nowadays, the test harness
runs each test in a subshell; but that's a well-known property of the
test harness so need not be mentioned explicitly.

Inspired by discussion on issue #443.

Also 'then'/'elif'/'else'.

Such a command word would, if not valid, fall through to the `type -w` case,
where the output would be misparsed, consequently the forward-compatible [arg0]
style would be used.