https://github.com/espressif/esp_iot_rtos_sdk/pull/19
I copied the closed-source libs into place and it seems to work - I can flash my ESP-01 and connect to its AP using my phone, get a DHCP address etc; and there's something listening on port 80, but I get no response from a browser or just telnetting to the port. Same happens in STATION mode - I can ping it, assign it a static ip, but nothing comes back from port 80. Seems I've got to figure out how to add a callback function to make the webserver return something.
Actually there's some lovely basic examples here: https://github.com/mattcallow/esp8266-sdk
I've now got 2 LED's blinking, STATION or SOFTAP wifi and printing system info over UART, all in 100 lines of C with 47k free heap!
Next, package it up so it doesn't all have to be a subdirectory of the sdk.