src/utils_dns.c: Rename the "s_addr" and "d_addr" variables.

src/utils_dns.c: Rename the "s_addr" and "d_addr" variables.

On Solaris, there is a macro called "s_addr" resulting in syntax errors
when this is used as a variable name. The variables have been renamed to
circumvent this problem. Thanks to Maciej Bliziński for reporting this
problem and helping to debug it!