Mark "private use area" characters as printable.

At least some of the characters in E000-F8FF range are used by Powerline
fonts, and having no attributes for these ranges in UnicodeData.txt
other than "Other, Private Use" it should be safe to mark all of them as
printable. Some actually were before r340491, so this fixes the
regression introduced there as well.

PR: 240911
Reviewed by: bapt
Tested by: Daniel Ponte <amigan@gmail.com>
Differential Revision: https://reviews.freebsd.org/D21850