Second try: Introduce plugin_crt0.c that every plugin links.

It handles exit() properly, calling the handler also when the plugin returns
normally (also make exit() more standard compliant while at it).
It also holds PLUGIN_HEADER, so that it doesn't need to be in each plugin anymore.

To work better together with callbacks passed to rb->default_event_handler_ex() introduce exit_on_usb() which will call the exit handler before showing the usb screen and exit() after it.
In most cases rb->default_event_handler_ex() was passed a callback which was manually called at all other return points. This can now be done via atexit().

In future plugin_crt0.c could also handle clearing bss, initializing iram and more.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27873 a1c6a512-1295-4272-9138-f99709370657

apps/plugins/lua/rocklua.c

@@ -20,7 +20,6 @@
  ****************************************************************************/
 
 #include "plugin.h"
-#include "lib/pluginlib_exit.h"
 #include "lua.h"
 #include "lauxlib.h"
 #include "lualib.h"
@@ -28,7 +27,7 @@
 #include "rockmalloc.h"
 #include "luadir.h"
 
-PLUGIN_HEADER
+
 
 static const luaL_Reg lualibs[] = {
   {"",              luaopen_base},
@@ -148,8 +147,6 @@ enum plugin_status plugin_start(const void* parameter)
     const char* filename;
     int status;
 
-    PLUGINLIB_EXIT_INIT
-
     if (parameter == NULL)
     {
         rb->splash(HZ, "Play a .lua file!");