Remove stub mirror driver code

We don't have any meaningful code for the mirror driver, so
remove the confusing stub and interface for it.
diff --git a/win/rfb_win32/SDisplay.cxx b/win/rfb_win32/SDisplay.cxx
index 26a7bbc..d4cedf8 100644
--- a/win/rfb_win32/SDisplay.cxx
+++ b/win/rfb_win32/SDisplay.cxx
@@ -29,7 +29,6 @@
 #include <rfb_win32/MonitorInfo.h>
 #include <rfb_win32/SDisplayCorePolling.h>
 #include <rfb_win32/SDisplayCoreWMHooks.h>
-#include <rfb_win32/SDisplayCoreDriver.h>
 #include <rfb/Exception.h>
 #include <rfb/LogWriter.h>
 
@@ -173,9 +172,7 @@
   int tryMethod = updateMethod_;
   while (!core) {
     try {
-      if (tryMethod == 2)
-        core = new SDisplayCoreDriver(this, &updates);
-      else if (tryMethod == 1)
+      if (tryMethod == 1)
         core = new SDisplayCoreWMHooks(this, &updates);
       else
         core = new SDisplayCorePolling(this, &updates);
@@ -234,10 +231,6 @@
   return WMHooks::areAvailable();
 }
 
-bool SDisplay::isDriverAvailable() {
-  return SDisplayCoreDriver::isAvailable();
-}
-
 
 bool SDisplay::isRestartRequired() {
   // - We must restart the SDesktop if: