localedef: define characters in "space" class also as "print", except
for the known conflicts ("control" characters can't be "print"able).
POSIX doesn't explicitly forbid this, and actually includes <space>
character in "print".

PR: 225692
Reviewed by: bapt, cem (previous version), pfg (previous version)
Approved by: kib (mentor)
Differential Revision: https://reviews.freebsd.org/D17467