PATCH: DNS Error messages

IMHO, there is a small glitch in HTDNS.c. Name Resolver errors do not get
reported via the standard error variable errno (and cannot be translated
using strerror). Thus, when a resolver error is encountered, the last
"real" system error gets reported, but not the proper resolver error.

The attached patch replaces the error message handling in HTDNS.c and
uses the hstrerror() function to obtain the message.

I would like to ask people to check the patch, especially the part that
deals with thread-safe resolver routines.

One problem that I see is that my glibc documentation mentiones that
hstrerror is obsolete, without giving any information about a replacement. 

The patch is against the current CVS and should be applied in Library/src.

peter