[Ironruby-core] Float parsing is culture dependent (patch included)

[Thibaut Barrère]

I ran rake specs. Before my patch, it blew up at
core/struct/each_pair_spec.rb (the very beginning).
After applying the patch, I get this amount of failures:

Total failures: 347 out of 1029 examples

Not sure how this compares to an english machine ?

Running "rake test" also blew up just after Dir tests. Applying the
patch managed to let the runner reach third test of StringScanner#new
(which blows up and makes rake abort).

If someone would like to get the full "rake specs" output, drop me a
line (it's 370kb long - I thought I wouldn't send it to the list
directly).

cheers

-- Thibaut