Changes 1.18.0:
lib: Accept and ignore content-length: 0 in 204 response for now
build: Use pkg-config to detect libxml2
build: Require c-ares to compile applications under src
build: Add Windows CI via AppVeyor (Patch from Alexis La Goutte)
examples: Delete tiny-nghttpd
nghttpx: Retry h1 backend request if first write fails (GH-757)
nghttpx: Keep reading after backend write failed (GH-756)
nghttpx: Add frontend-keep-alive-timeout option (GH-755)
nghttpx: New error log format (GH-749)
nghttpx: Fix bug that fetch-ocsp-response does not work with OpenSSL 1.1.0 (GH-742)
nghttpx: Backend API call allows non-numeric host with dns parameter (GH-731)
nghttpx: Lookup backend host name dynamically (GH-721)
nghttpx: Accept and ignore content-length: 0 in 204 response for now (GH-735)
nghttpx: Wait for child process to exit

(adam)