x11/xmodmap: Update to 1.0.10

Update x11/xmodmap to 1.0.10
Add license file

This release provides a man page update and some small build fixes &
janitorial cleanups.

Changelog:
https://lists.x.org/archives/xorg/2019-February/059615.html

PR: 236089
Submitted by: Samy Mahmoudi