Floating point formatting

[Martin Stjernholm, Roxen IS @ Pike developers forum]

I plan to fix this, since I consider it a gross bug:

  > Gettext.setlocale (Gettext.LC_NUMERIC, "sv_SE.UTF-8");
  (1) Result: 1
  > (string) 3.14;
  (2) Result: "3,14"
  > sprintf ("%O", 3.14);
  (3) Result: "3,14"

I.e. casting and %O are locale sensitive and doesn't always produce a
decimal point.

Would it conceivably be a compatibility problem to just fix this right
away in 7.8? It would not affect %f, %g and all the other floating
point formatters.