* Fixing issue #15302 -- lwip doesn't support signals
* Adding test to catch issue #15302 -- lwip/freertos net library
don't try to build / run on windows, it'll compile only but not run
Fixing issue #15302 -- reworking test to compile on other platforms
* Changes for FreeRTOS/LwIP Port for the ESP32 (ESP-IDF)
Adding FreeRTOS/LwIP to compiler:
* adding freertos option
* dyncalls for freertos
* add freertos to posix os list
* adding lwip option
Setting up networking FreeRTOS/LwIP Port:
* setting up lwip network for freertos
* fixing posix / networking for freertos
* disable setInheritable for freerots
* using lwip for net control items
* Fix builds by ignoring lib/posix/posix_freertos_consts.nim similar to lib/posix/posix_other_consts.nim
