gnuplot: bump version to 5.0.5

- 0001-configure-add-without-demo-option.patch adapted to new version.
- --without-lisp-files configure option removed: doesn't exist anymore.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>