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
13 files changed