Serge's ei float patch

[Steve Vinoski]

This is a submission of Serge Aleynikov's ei patch that implements
binary encoding for floats:

git fetch git://github.com/vinoski/otp.git serge_new_float_ext

Note there are two commits on this branch: 3b3bae9 and a1ae64e. One
just fixes a typo in the ei_decode_ei_term documentation -- I kept
that commit separate since it's independent. The other commit is
Serge's original R12B-2 patch adjusted as needed for the current code
base and with the addition of fixing all areas across Erlang/OTP
affected by the change. The only exception is that I didn't change
erl_marshal.c because it's "legacy" so I'm not sure it has to handle
this new encoding or not.

If anyone wants to see the exact changes for each commit, the links to
the two commits are:

http://github.com/vinoski/otp/commit/3b3bae9397b405ce5e782d684ed88e0442eab65e
http://github.com/vinoski/otp/commit/a1ae64e5c30f89a2c6b9d1b83777a72235ffc003

--steve