Change configure test for getaddrinfo

The problem is that with the default AC_REPLACE_FUNCS, autoconf declares it as
"char getaddrinfo(void)". However on Windows, because of stdcall calling
convention, the symbol emitted differs because of the missing calling
convention directive and the different the number of arguments.

See http://lists.gnu.org/archive/html/autoconf/2013-05/msg00085.html for more
info.
Make the getaddrinfo check even simpler.

Amending the previous commit, this one removes completely the linking test for
getaddrinfo. So to replace the function, it is enough now for the platform to
be missing getaddrinfo declaration.
Merge pull request #687 from jimis/win32

Fix for MinGW 32-bit build.