Build Apache on Vista

It's reported that APR fails to compile on Vista with the latest SDK. This is due to the new macro MCAST_JOIN_SOURCE_GROUP in Vista. The workaround is quite simple:
1. open the generated apr.h;
2. set _WIN32_WINNT to 0x0600;
3. set APR_HAVE_IPV6 to 1 (or there would be a link error with the function find_if_index).

Btw, just got back to Beijing this morning. Well, there's rather a lot of work to do.

Update1: ASF Bugzilla Bug 40398
Update2: APR 1.2.9 on Vista