Missing includes in arpa/inet.h

Hi!

I'm working on ecos and realized that arpa/inet.h does not include
header files that define the data structures used. eg: struct in_addr.

I was wondering if this was by-design or wether it is just oversight.

I'd like to fix these since i need a proper include chain for my 
current toolchain.

Other files where this is the case:

sys/endian.h
arpa/nameser.h
bootp.h

Best Regards,
Guilherme