remove cruft from old resolver and numeric ip parsing

the old resolver code used a function __ipparse which contained the
logic for inet_addr and inet_aton, which is needed in getaddrinfo.
this was phased out in the resolver overhaul in favor of directly
using inet_aton and inet_pton as appropriate.

this commit cleans up some stuff that was left behind.

fix argument types for legacy function inet_makeaddr

the type int was taken from seemingly erroneous man pages. glibc uses
in_addr_t (uint32_t), and semantically, the arguments should be
unsigned.

fix regression in inet_aton due to misinterpretation of __ipparse return

inet_aton returns a boolean success value, whereas __ipparse returns 0
on success and -1 on failure. also change the conditional in inet_addr
to be consistent with other uses of __ipparse where only negative
values are treated as failure.

fix inet_aton to accept the generic "numbers-and-dots" IPv4 address format

split inet_addr and inet_ntoa back into their own files

despite being practically deprecated, these functions are still part
of the standard and thus cannot reside in a file that also contains
namespace pollution. this reverts some of the changes made in commit
e40f48a421a9176e3e298b5bac75f0355b219e58.

implement inet_lnaof, inet_netof, and inet_makeaddr

also move all legacy inet_* functions into a single file to avoid
wasting object file and compile time overhead on them.

the added functions are legacy interfaces for working with classful
ipv4 network addresses. they have no modern usefulness whatsoever, but
some programs unconditionally use them anyway, and they're tiny.