CMake: Use 'findPkgVersion' to find the version of Cerf package under Windows

cmake/find/FindCerf.cmake

@@ -26,7 +26,13 @@ if(NOT WIN32)
     endif()
   endif()
 else()
-  set(Cerf_VERSION "")
+  include(FindPkgVersion)
+  findPkgVersion(
+    "cerf"  # libname
+    ""  # use default config file
+    "${CMAKE_LIBRARY_PATH}"  # search paths
+    Cerf_VERSION  # output variable
+    )
 endif()
 
 find_path(Cerf_INCLUDE_DIR cerf.h)