msgdef: fix NO and SI locales

Fix circular symlinks by providing separate source for nn_NO.ISO8859-1,
nn_NO.ISO8859-15, and sl_SI.ISO8859-2 (re)generated from CLDR.

PR: 260841
Reviewed by: imp (previous version)
Fixes: 0a36787e4c1f ("locales: separate unicode from other locales")
Differential Revision: https://reviews.freebsd.org/D41899