VC build patch

I have posted a first "almost complete" version of the vc build system to -patches. Those interested in building pg (everything, not just the client) with Visual C++ 2005 should check it out, and let me know of any issues.

For details, see -patches. Super-quick summary: VC++ patch will allow us to properly integrate with windows debuggers, profilers and such tools. And it will take away the dependency on mingw/msys to build. Hopefully, it will also be a nice path towards Win64 support.

And for those who're worried - no, mingw support is definitly not going away.

Along with this, I've also posted an initial port of pg_regress to C, which will be required to run the regression tests without mingw/msys. Feel free to check that one out as well...