irs.h

[Jun-ichiro itojun Hagino]

	is it really necessary to:
	- install irs.h, fd_setsize.h and res_update.h into /usr/include
	- making symbols like getservbyport_p to normal user
	they are internal to bind resolver, and struct net_data is not
	publically exported, i think it makes more sense to hide these symbols.
	i guess people will encounter problems in integrating BIND8 resolver
	into their product. (in fact, i'm having trouble in netbsd)

itojun