The pthread API is considered a standard feature of libc so better to
simply merge it with the libc. Pthreads are in fact already a part of
the libc in the form of weak symbols. This merger is also a prerequisite
for better integrating pthreads with the libc I/O task.
Fix#3054
This is a follow-up commit to "Increase default warning level", which
overrides Genode's new default warning level for targets contained in
higher-level repositories. By explicitly whitelisting all those targets,
we can selectively adjust them to the new strictness over time - by
looking out for 'CC_CXX_WARN_STRICT' in the target description files.
Issue #465