Skip locale test on OpenBSD, MirBSD and Bitrig too

From the original ticket #115808 the following should produce
"Use of uninitialized value in print at -e line 1."

$ perl -wle 'use POSIX; print length setlocale POSIX::LC_ALL, "mtfnpy"'
16

So skip this test on OpenBSD, MirBSD and Bitrig