mxcl/homebrew — pull request #9003 by hydra5 (2011-12-06 19:56:49+00:00)
Title: Fix to enable compiling on Mac OS X Lion (isc-dhcp)

adding line 34-37:

if 10.7 <= MACOS_VERSION
ENV.append 'CFLAGS', "-D__APPLE_USE_RFC_3542"
end

solves it

Ticket: https://gist.github.com/1157223