We do not need to define _WIN32 by hand; MSVC does that for us

Bug 5858; fix on 0.2.3.12-alpha

changes/bug5858

@@ -0,0 +1,4 @@
+  o Minor bugfixes:
+    - Remove bogus definition of "_WIN32" from src/win32/orconfig.h, to
+      unbreak the MSVC build. Fies bug 5858; bugfix on 0.2.3.12-alpha.
+

src/win32/orconfig.h

@@ -3,7 +3,6 @@
  */
 
 /* Windows-only defines. */
-#define _WIN32
 #define CONFDIR ""
 
 /* Define to 1 if you have the <arpa/inet.h> header file. */