Revert "automagically determine if to set wxplot_pngcairo."

This reverts commit f2ac74645323500ada2e1979406917690f94aee0:
Will move it to a branch.
Revert "Make maxima's new line styles work."

This reverts commit 50ad7401a4fbbe3ae212f902a4d8b1461978805b:
Will move it to a branch.
Will move this commit to a branch.

Revert "Revert "Make maxima's new line styles work.""

This reverts commit def8b5fdfa0eda2de8ab650d6bf528e7caa3f92d.
Will move it to a branch.

Revert "Revert "automagically determine if to set wxplot_pngcairo.""

This reverts commit edc7d373753f3dd41939bae73a4b002329b7bc47.