The ebuild seems to be missing SRC_URI arrows to rename the distfile: 82eb9752485db87c9c6d3d6bb4aa1ae7ac81174a.zip
you can drop x11vnc-0.9.13_p20150111, stable was finished long ago.
commit 487377a532ca955416a2dfea5b30344fd7dd554e (HEAD -> master, origin/master, origin/HEAD) Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Sun May 28 09:18:39 2017 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Sun May 28 09:18:39 2017 x11-misc/x11vnc: Clean old up, #619894