FIX! ..temporary files handling! And rewrite Ftmp()..

FIX! ..temporary files handling!  And rewrite Ftmp()..

Yet another fallout of the large NYD series in February 2014, this
time of [fff6528], where we completely reimplemented the handling
of temporary files at the same time.
Yep, another one.

  Since February 2014 (18 months!?!) we do create temporary files
  in the current directory instead of "tempdir"!!!!
  8-P
  Bummer!!!

So now that we have had (Fix CLOEXEC bit for temporary
descriptors.., just a few minutes ago) let's just step ahead and
rewrite Ftmp() not to use these CRAPPY mktemp(3), mkstemp(3) or
mkostemp(3) series, but do it ourselfs instead.
Thank you.