[core] use kqueue in level-triggered mode (fixes #2788)
[core] use kqueue in level-triggered mode (fixes #2788)

use kqueue in level-triggered mode, not edge-triggered

x-ref:
  "FreeBSD/1.4.45/SSL: requests getting stuck in handle-req state occasionally"
  https://redmine.lighttpd.net/issues/2788

PatchyFog/lighttpd1.4-mbedtls,gstrauss/lighttpd1.4,PatchyFog/lighttpd1.4-mbedtls,PatchyFog/lighttpd1.4-mbedtls,PatchyFog/lighttpd1.4-mbedtls,lighttpd/lighttpd1.4,PatchyFog/lighttpd1.4-mbedtls,PatchyFog/lighttpd1.4-mbedtls,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,PatchyFog/lighttpd1.4-mbedtls,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4