Fix for R16B's removal of paramaterized modules

Copy OTP's paramaterized module parse-transform
(https://github.com/erlang/pmod_transform) into the source tree;
add compiler pragmas to files that require parameterized modules
to use the parse-transform (sockjs_pmod_pt).

The module implementing the parse-transform has been renamed, as
per OTP's suggestion, to avoid name clashes.