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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.

Fixes #480.

The new failure mode is:
.
    Running test main
    Bail out! On './highlighters/main/test-data/glob.zsh': Either 'PREBUFFER' or 'BUFFER' must be declared and non-blank
    Bail out! On './highlighters/main/test-data/glob.zsh': output on stderr
    Running test pattern

Fixes #478.

Found-by: Matthew Martin

Closes #468.

Closes #277.

Closes #130

Closes #466.

Closes #441.

Unbreaks build on pre-5.4.

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.

Closes #458.

Closes #112. Closes #138.

Unbreak build for 5.0.8 and earlier.

Closes #382.