rename build_define_cflag to build_cflag_d since CFLAG_D is a wrapper to it
rename build_define_cflag to build_cflag_d since CFLAG_D is a wrapper to it

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