Behave same on BSDs as on Darwin in that UTF-8 shall be used instead of
ASCII outside the POSIX 'C' locale and UTF-8 is deafult in case anything
should call ucnv_getDefaultName() prior to calling setlocale(). This change
fixes problems that occur in multiple Qt5 applications when handling files
with names containing non-ASCII characters.

PR: 216372
Reported by: vvd@unislabs.com
Approved by: bapt (office@), swills (mentor)
Differential Revision: https://reviews.freebsd.org/D10128