Provide a patch to fix building when the non default option SIXEL is enabled
without the REGIS option. This does not affect default options and therefore
no PORTREVISION bump is required. This regression does not affect the quarterly
branch therefore no MFH is required.

PR: 219945 (based on)
Submitted by: ashish@FreeBSD.org, Thomas Dickey <dickey@his.com> (author)