Change the thread api a bit.

* Remove THREAD_ID_CURRENT macro in favor of a thread_self() function, this allows thread functions to be simpler.
* thread_self_entry() shortcut for kernel.c.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29521 a1c6a512-1295-4272-9138-f99709370657

apps/plugin.c

@@ -779,6 +779,7 @@ static const struct plugin_api rockbox_api = {
 
     /* new stuff at the end, sort into place next time
        the API gets incompatible */
+    thread_self,
 };
 
 int plugin_load(const char* plugin, const void* parameter)