applied patch #1912699 - "Pinned" / always loaded plugins support

this patch also adds plugin_api_version to exec_flags so your plug-in can now tell if features it needs are available
more plug-ins that need this will be converted once the patch to make both the stubs and the plug-ins use the same header file is in place

git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@5809 212acab6-be3b-0410-9dea-997c60f758d6

Source/exehead/Main.c

@@ -25,6 +25,7 @@
 #include "lang.h"
 #include "state.h"
 #include "exec.h"
+#include "plugin.h"
 
 #if !defined(NSIS_CONFIG_VISIBLE_SUPPORT) && !defined(NSIS_CONFIG_SILENT_SUPPORT)
 #error One of NSIS_CONFIG_SILENT_SUPPORT or NSIS_CONFIG_VISIBLE_SUPPORT must be defined.
@@ -341,6 +342,8 @@ void NSISCALL CleanUp()
     dbd_hFile = INVALID_HANDLE_VALUE;
   }
 #endif
+  // Notify plugins that we are about to unload
+  Plugins_UnloadAll();
 #ifdef NSIS_CONFIG_PLUGIN_SUPPORT
   // Clean up after plug-ins
   myDelete(state_plugins_dir, DEL_DIR | DEL_RECURSE | DEL_REBOOT);