x11/libfm, x11-fm/pcmanfm: update and flavorize both.

• update x11/libfm to version 1.3.1
• update x11-fm/pcmanfm to version 1.3.1
• convert both to flavors
• fix other affected ports

PR: 229944
Reviewed by: adamw, antoine, bapt
Approved by: mat (portmgr, mentor), tcberner (mentor), jsm (maintainer), Chris Hutchinson <portmaster@bsdforge.com> (maintainer)
Differential Revision: https://reviews.freebsd.org/D16387