slic3r: Add LWP for "Send to printer"
This patch adds a dependency on the LWP perl module so that Slic3r can
make HTTP connections to Octoprint and send G-code to a remote printer.
(cherry picked from commit f303a072c02d5659abc8b03e69f98f789745b4ab)
authored by Peter Jones and committed by Bjørn Forsman f231b2b3 ec0889d3