Fix a backward compatibility bug with inet:parse_strict_address/1

inet:parse_strict_address/1 was introduced in R16. For previous releases, we
need to rely on inet_parse:ipv4strict_address/1 and
inet_parse:ipv6strict_address/1 functions.
Do not set recbuf by default on listening sockets

This patch removes a bug I experienced on FreeBSD during tests on the loopback
interface because of its MTU. So, I don't really know why that happens on
FreeBSD and not on Linux, but because loopback MTU is greater than the recbuf
value (16K on loopback vs 8k in Yaws), if a client sends data, Yaws will read
them very slowly.

Furthermore, there is no good reason to tweak this value by default. And, if
required, it is always possible to configure it.
Add yaws:hup/0 to allow Yaws reloads from another erlang module
Handle a bug in unicode module in releases R14B04 and previous

The code points 16#FFFE and 16#FFFF (not assigned but valid) are considered
invalid for releases R14B04 and previous. So for these releases, the websockets
testsuite always failed. No, it is fixed.

It was fixed in OTP with the commit 34db767655:
   https://github.com/erlang/otp/commit/34db767655
Update known dialyzer warnings