fix find windows.h for winsdk8

--HG--
branch : cmake-fixes

code/CMakeModules/FindWindowsSDK.cmake

@@ -165,9 +165,13 @@ MACRO(USE_CURRENT_WINSDK)
   SET(WINSDK_VERSION_FULL "")
 
   # Use WINSDK environment variable
-  IF(WINSDKENV_DIR AND EXISTS ${WINSDKENV_DIR}/include/Windows.h)
-    SET(WINSDK_DIR ${WINSDKENV_DIR})
-  ENDIF(WINSDKENV_DIR AND EXISTS ${WINSDKENV_DIR}/include/Windows.h)
+  IF(WINSDKENV_DIR)
+    FIND_PATH(WINSDK_DIR Windows.h
+      HINTS
+      ${WINSDKENV_DIR}/Include/um
+      ${WINSDKENV_DIR}/Include
+    )
+  ENDIF(WINSDKENV_DIR)
 
   # Use INCLUDE environment variable
   IF(NOT WINSDK_DIR AND WINSDKCURRENT_VERSION_INCLUDE)
@@ -177,7 +181,7 @@ MACRO(USE_CURRENT_WINSDK)
       # Look for Windows.h because there are several paths
       IF(EXISTS ${_INCLUDE}/Windows.h)
         STRING(REGEX REPLACE "/(include|INCLUDE|Include)(.*)" "" WINSDK_DIR ${_INCLUDE})
-        MESSAGE(STATUS "Found Windows SDK environment variable in ${WINSDK_DIR}")
+        MESSAGE(STATUS "Found Windows SDK from include environment variable in ${WINSDK_DIR}")
         BREAK()
       ENDIF(EXISTS ${_INCLUDE}/Windows.h)
     ENDFOREACH(_INCLUDE)