[Dnsapi.dll] Implement Dnsapi.dll

[MattK]

This is a patch to implement Dnsapi.dll. It contains "bare bones".
This was done mainly to help with Bug 4323
<http://bugs.winehq.org/show_bug.cgi?id=4323>. This patch has the
DllMain entry point, a function and a stub, header files,
implementation into the tree, and a .spec file. Please tell me how to
correct anything if there is a problem.