misc/unclutter-xfixes: update to 1.6

Changelog
[Feature] --start-hidden to hide the cursor initially when unclutter-xfixes starts.
[Feature] --ignore-buttons to specify one or more buttons which do not unhide the cursor.
[Feature] --hide-on-touch to hide the cursor on touch input.
[Fix] --timeout now supports non-integer values.
Various improvements to the man page.

PR: 258066