LWIP part has been finally fully split from the ESP part, and ESP
platform defs reduced to bare minimum. It is now possible to use LWIP
in either low-level or socket mode without any ESP dependencies,
and NXP Kinetis platform is the first to make use of it.
PUBLISHED_FROM=4a9055897609c812296bdab5b4943ffde641ced2
Factor out SSI and WS code from http.c
HTTP + WS are enabled by default, but MQTT is built without HTTP
support as a compilation test.
PUBLISHED_FROM=925ed9a55abb193ed7deac1c9675a0e5b35dca50
