Merge p1_fsm and p1_server with latest gen_server and gen_fsm

[mremond]

We need to merge our changes, but also update license (Erlang OTP is under Apache 2.0 license now).

It will also help remove deprecation:

src/p1_fsm.erl:605: Warning: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.
src/p1_fsm.erl:610: Warning: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.
src/p1_fsm.erl:668: Warning: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.
src/p1_fsm.erl:673: Warning: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.

However, we may need to have to support both R17 and R18.