lib/util: Add functions to escape log lines but not break all non-ascii

lib/util: Add functions to escape log lines but not break all non-ascii

We do not want to turn every non-ascii username into a pile of hex, so we instead focus
on avoding newline insertion attacks and other low control chars

Pair-programmed-by: Andrew Bartlett <abartlet@samba.org>
Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Signed-off-by: Andrew Bartlett <abartlet@samba.org>