WL#5363: Thread Pool Service Interface

In order to allow thread schedulers to be dynamically loaded,
it is necessary to make the following changes to the server:

- Two new service interfaces

- Modifications to InnoDB to inform the thread scheduler of state changes.

- Changes to the VIO subsystem for checking if data is available on a socket.

- Elimination of remains of the old thread pool implementation.

The two new service interfaces introduces are:

my_thread_scheduler
  A service interface to register a thread
  scheduler.

thd_wait
  A service interface to inform thread scheduler
  that the thread is about to start waiting.

In addition, the patch adds code that:

- Add a call to thd_wait for table locks in mysys
  thd_lock.c by introducing a set function that
  can be used to set a callback to be used when
  waiting on a lock and resuming from waiting.

- Calling the mysys set function from the server
  to set the callbacks correctly.

mysys/my_init.c

@@ -499,7 +499,7 @@ static my_bool win32_init_tcp_ip()
 {
   if (win32_have_tcpip())
   {
-    WORD wVersionRequested = MAKEWORD( 2, 0 );
+    WORD wVersionRequested = MAKEWORD( 2, 2 );
     WSADATA wsaData;
  	/* Be a good citizen: maybe another lib has already initialised
  		sockets, so dont clobber them unless necessary */