x11/xfce4-terminal: Fix configuration option not working properly

The terminal configuration has an option to disable F10 key grabbing
to control drop down menus. Since the update to 1.1.0 this option
is broken, not allowing the F10 key to be passed to the terminal
correctly.

This patch imports an upstream patch to fix the issue.

While here:

• Remove unneeded dependency on libxml2
• Move INSTALL_TARGET variable to pet portclippy

PR: 273742
Obtained from: https://gitlab.xfce.org/apps/xfce4-terminal/-/commit/c576281a780884f9ba1f6abe3d543a3a00f0b48d