picky compiler warnings

PORT
Provide better error messages to allow debugging if one if the ipv6-related
name functions fail in the ftp_use_port() function. This might help us
diagnose the problems on AIX. Also make sure getaddrinfo() uses NULL and
not "0" for the service argument.

as then we include the memdebug.h header from the lib dir, and it then
requires this type... (fails on IRIX 6.5 without this)

about it shadowing the function sin()

added prototypes for the strcasecmp() functions

that assume them to be unsigned. Stops compiler warnings.

warnings

support --enable-debug to switch on picky compiler options

and the original ares installed in the same lib dir.

response reading function

make this better on more systems.

utility