use win32 threads for win32

Modules/CMakeVS6BackwardCompatibility.cmake

@@ -8,3 +8,4 @@ SET (CMAKE_SIZEOF_FLOAT     4   CACHE INTERNAL "Size of float data type")
 SET (CMAKE_SIZEOF_DOUBLE    8   CACHE INTERNAL "Size of double data type")
 SET (CMAKE_NO_ANSI_FOR_SCOPE 1 CACHE INTERNAL 
          "Does the compiler support ansi for scope.")
+SET (CMAKE_USE_WIN32_THREADS  TRUE CACHE BOOL    "Use the win32 thread library.")

Modules/CMakeVS7BackwardCompatibility.cmake

@@ -8,3 +8,4 @@ SET (CMAKE_SIZEOF_FLOAT     4   CACHE INTERNAL "Size of float data type")
 SET (CMAKE_SIZEOF_DOUBLE    8   CACHE INTERNAL "Size of double data type")
 SET (CMAKE_NO_ANSI_FOR_SCOPE 0 CACHE INTERNAL 
          "Does the compiler support ansi for scope.")
+SET (CMAKE_USE_WIN32_THREADS  TRUE CACHE BOOL    "Use the win32 thread library.")