Support github options extra_lines/extra_lines_after_os_dependencies

[mauritsvanrees]

extra_lines was already passed on to the test matrix, but not used. extra_lines_after_os_dependencies is needed for Products.CMFPlone to configure a locale, needed for one test.

This is needed in CMFPlone, otherwise you get a few test failures:

ValueError: Unsupported locale.
These tests need at least one of the following locales available on your system:
('en_US.ISO-8859-1', 'en_US.ISO8859-15', 'en_GB.ISO8859-15',
'de_DE@euro', 'fr_FR@euro', 'nl_NL@euro')

I use this in the CMFPlone src-layout PR, in this commit. And the try to fix it in this second commit. And that seems to help.

[gforcada]

LGTM! 👍🏾