Upstream notes that this is a bugfix release, so we may hope that it is an easy bump. http://www.gnuplot.info/ReleaseNotes_5_0_3.html
commit ce9db67160a1de82244c6dc078b90320672491a7 Author: Christoph Junghans <ottxor@gentoo.org> Date: Mon Mar 7 09:11:08 2016 -0700 sci-visualization/gnuplot: version bump (bug #576710) Package-Manager: portage-2.2.26