graphics/xfig: update to 3.2.8b

ChangeLog: https://sourceforge.net/p/mcj/xfig/ci/master/tree/CHANGES

This update also fixes the build in 14.

BUGS FIXED:

• Adding points to splines works if boxes are present in the figure.
• Stay in the working directory when browsing picture files.

PR: 273130
Reported by: mjl@luckie.org.nz (maintainer)