This reverts commit 5f5a981d.  Coverity warning
about mkstemp without umask appears to be bogus (cf.
<https://communities.coverity.com/message/6516> "Why are uses of mkstemp
'without securely setting umask first' being flagged?) and calling umask is not
MT-safe, see fdo#60338 "FILESAVE: Saved files have incorrect permissions on
linux."