[fuzzer] Always define H2O_USE_EPOLL in fuzzer modules
[fuzzer] Always define H2O_USE_EPOLL in fuzzer modules

Otherwise some module may see a different structure layout which
results in buffer overrun etc.

h2o/h2o,cwyang/h2o,cwyang/h2o,devnexen/h2o,devnexen/h2o,devnexen/h2o,cwyang/h2o,yannick/h2o,cwyang/h2o,cwyang/h2o,h2o/h2o,devnexen/h2o,yannick/h2o,h2o/h2o,h2o/h2o,yannick/h2o,cwyang/h2o,yannick/h2o,devnexen/h2o,h2o/h2o,h2o/h2o,devnexen/h2o,yannick/h2o,h2o/h2o,cwyang/h2o,yannick/h2o,cwyang/h2o,h2o/h2o,yannick/h2o,devnexen/h2o,h2o/h2o,yannick/h2o,yannick/h2o,devnexen/h2o,devnexen/h2o