Application developers use `$(USEMODULES)` in their Makefiles to have
the relevant functionally automagically added to their apps. This even
does basic dependency tracking by means of `Makefile.dep`.
But an important thing is missing: the automatic adding of include
paths. This is inconvenient, error prone, and will hinder the RIOT core
developers in future to change folder structures.
This fixes#755.
The pthread ID cannot be reused as soon as the thread ends, because
another thread needs to join it first. `pthread_self()` uses the native
(i.e. RIOT's) thread ID to distinguish itself. A native thread ID can be
reused as soon as the thread ends, since the core knows no join
operation.
In order to not confuse itself with an earlier zombie thread (i.e a dead
non-detached thread, that was not joined, yet), we need to invalidate
the associated native thread ID.
This approach is sane since a dead thread won't call `pthread_self()`
anymore.