Always check that mktemp()/mktemp2() succeeds before trying to

Always check that mktemp()/mktemp2() succeeds before trying to
use result.  And if it fails, have the error message report
the directory where the failed temporary file creation occurred.
And, removed all chmod()'s of temporary files created by mktemp()/
mktemp2() because they set the umask to 077 before calling mkstemp(3).