switch to R16 for 3.0 (was: investigate possibility of switching to R16B03)

Updating erlang will fix some issues (there's at least one windows issue that states that we're waiting for R16).

R16 can also have 64-bit erlang VM on windows which might be somewhat important for use-cases that "require" erlang to have tons of memory (32-bit vm dies at about 2 gigs of memory eaten on windows).

R1603 also has +MMscs (supercarrier something...) which might be useful for memory tuning.

There's however known downsides (at least):

• I think we've had data that R15 and R16 is slower on our use-cases

• R16's ssl is quite broken. At least with it's implementation of elliptic curves DH exchange. Might be fixable by disabling it.