This makes it possible to compile cfws with Visual Studio. Since winsock
and POSIX use very similar APIs, porting is mostly just a matter of
placing ifdefs around #includes and functions with slightly different
names.

However, CGI scripts and command line arguments are not available in
this port yet, since they used the Unix-exclusive getopt.h and popen.

Building each source file as a separate object makes it faster to
compile when only changing one source file, and also allows you to
compile with multiple threads when building the whole project.