www/elinks: Update to 0.18.0

Drop the libCSS/libdom patch as it's not needed anymore.
Removes options that don't require a library installed from a package
(except for EXMODE/LOCAL_CGI/NOROOT)
Wire in the test suite.
Add MUJS, PYTHON, and SIXEL options.

PR: 281909
Approved by: submitter is maintainer