vcbuild updates from Magnus:

* After Markos patch, now builds pgcrypto without zlib again
* Updates README with xml info
* xml requires xslt and iconv
* disable unnecessary warning about __cdecl()
* Add a buildenv.bat called from all other bat files to set up things
like PATH for flex/bison. (Can't just set it before calling, doesn't
always work when building from the GUI)

src/tools/msvc/Project.pm

@@ -23,7 +23,7 @@ sub new {
         includes        => '',
         defines         => ';',
 		solution        => $solution,
-        disablewarnings => '4018;4244',
+        disablewarnings => '4018;4244;4273',
     };
 
 	bless $self;