BuildSystem/Windows: * Added 5.1.50 (GA) MySQL client sources for crosscompiling (or lazy) windows people.

* Added an option to autosearch for your own installed MySQL as before. Note that default setting is to use the internal MySQL.
* You can now build 32-bit even if your MySQL is x64 and vice versa.
* Recommended MySQL server version for use with provided MySQL client sources is 5.1.x.
* If your server version is different, let CMake autofind and use it instead (check EXTERNAL_MYSQL option)

--HG--
branch : trunk

cmake/showoptions.cmake

@@ -63,6 +63,15 @@ else()
   message("* Use SFMT for RNG       : No  (default)")
 endif()
 
+if( WIN32 )
+  if( EXTERNAL_MYSQL )
+    message("* Use external MySQL     : Yes")
+    add_definitions(-DUSE_SFMT_FOR_RNG)
+  else()
+    message("* Use external MySQL     : No  (default)")
+  endif()
+endif( WIN32 )
+
 if( WITH_WARNINGS )
   message("* Show all warnings      : Yes")
 else()