List of 3rd party modules github repositories was obtained from
https://github.com/freebsd/freebsd-ports/blob/main/www/nginx-devel/Makefile.extmod

List of 3rd party modules github repositories are obtained from
https://github.com/freebsd/freebsd-ports/blob/main/www/nginx-devel/Makefile.extmod

Line continuation as used in the syntax file might be broken if "compatible"
is set or "C" is added to cpoptions.  Fix is to set the "cpoptions" option
to vim default value at script start and restore it later, see
":help use-cpo-save".

Using default highlighting makes it possible to easily overrule
highlighting specified in the syntax file, see ":highlight-default"
in vim help for details.

Add new directives for 3rd party modules.

"match" is block directive, "upstream_conf" is deprecated
by patch http://hg.nginx.org/nginx.org/rev/27c53e1cb4b6

Removed non-existent directives and directive redefinitions.

3rd party modules list synchronized with FreeBSD nginx-devel port.

Non-quoted parameters are allowed to contain variables in curly brackets
(see d91a8c4ac6bb), so vim syntax rules were adjusted accordingly.

Instead of highlighting directives in arbitrary positions, proper
parsing of nginx.conf syntax was implemented, matching what nginx does
internally.  This allows vim to correctly highlight various complex cases,
including:

    return 301 http://example.com/path#fragment";

and also avoids highlighting of parameters as directives, as in

    server_name missing.semicolon.example.com
    index index.php;

where "index" is not a directive but a parameter of the "server_name"
directive due to missing semicolon.

Most important downside of this approach seems to be that there is no
easy way to introduce directive-specific parameters.  As such, only "listen"
directive parameters were preserved.