[core] avoid repeated typedef for fdlog_st
[core] avoid repeated typedef for fdlog_st

x-ref:
  "Lighttpd 1.4.60 make error typedef fdlog_st redefinition"
  https://redmine.lighttpd.net/boards/3/topics/10043

gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4