Always compile with __NT__ on windows. in 5.1 itthis #define is

widely used, in replication (delete_allow_opened) and for named
pipe support. We do not support Win9x anymore.

CMakeLists.txt

@@ -45,9 +45,9 @@ CONFIGURE_FILE(${CMAKE_SOURCE_DIR}/support-files/my-medium.cnf.sh
 CONFIGURE_FILE(${CMAKE_SOURCE_DIR}/support-files/my-small.cnf.sh
                ${CMAKE_SOURCE_DIR}/support-files/my-small.ini @ONLY)
 
-IF(__NT__)
-  ADD_DEFINITIONS(-D__NT__)
-ENDIF(__NT__)
+
+ADD_DEFINITIONS(-D__NT__)
+
 IF(CYBOZU)
   ADD_DEFINITIONS(-DCYBOZU)
 ENDIF(CYBOZU)