Recent TNonblockingServer changes broke --enable-boostthreads=yes, Windows

Following the (nice) improvements for TNonblockingServer in THRIFT-1442, this patch restores both --enable-boostthreads=yes, and the Windows build.

Included in this patch:

• Add more HAVE_CONFIG_H includes
• Replace PosixThreadFactory by PlatformThreadFactory where appropriate
• Abstract away pthread vs boost::thread inside Thread.h, adding new methods is_current/get_current
• Renamed INVALID_SOCKET, caused compilation problems on Windows (already defined in WinSock2.h)
• Restore back more portable evutil_socketpair (in place of pipe, for Windows)
• Add evutil_make_socket_nonblocking (as of THRIFT-1442)

Also included (minor):

• Add x64 target to VisualC++ compiler
• Fix minor glitch in bison/compiler for VisualC++
• Remove more VisualC++ warnings

This was tested on Ubuntu 10.10, Boost 1.44, Libevent 2.0.16, Visual C++ 10.