Drop #defines to target Windows 2000 or later

lib/zipint.h

diff --git a/lib/zipint.h b/lib/zipint.h
index 936ea33..edfc455 100644
--- a/lib/zipint.h
+++ b/lib/zipint.h
@@ -63,7 +63,12 @@
 #define false   0
 #endif
 
+#ifdef HAVE_MOVEFILEEXA
+#include <windows.h>
+#define _zip_rename(s, t)	(!MoveFileExA((s), (t), MOVEFILE_COPY_ALLOWED|MOVEFILE_REPLACE_EXISTING))
+#else
 #define _zip_rename	rename
+#endif
 
 #ifdef _WIN32
 #if defined(HAVE__CLOSE)

lib/zipwin32.h

diff --git a/lib/zipwin32.h b/lib/zipwin32.h
index 6dba041..cc205dd 100644
--- a/lib/zipwin32.h
+++ b/lib/zipwin32.h
@@ -34,10 +34,6 @@
   IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-/* Target Windows 2000 and later */
-#define WINVER 0x0500
-#define _WIN32_WINNT 0x0500
-#define _WIN32_WINDOWS 0x0500
 #include <windows.h>
 
 /* context for Win32 source */