Using the new 'join()' function, the caller can explicitly block for the
completion of the thread's 'entry()' function. The test case for this
feature can be found at 'os/src/test/thread_join'. For hybrid
Linux/Genode programs, the 'Thread_base::join()' does not map directly
to 'pthread_join'. The latter function gets already called by the
destructor of 'Thread_base'. According to the documentation, subsequent
calls of 'pthread_join' for one thread may result in undefined behaviour.
So we use a 'Genode::Lock' on this platform, which is in line with the
other platforms.
Related to #194, #501
The Lua runtime library is built in two variants: ANSI C and C++. The
C++ provides all Lua API function with C++ linkage and uses C++
exceptions instead of setjmp/longjmp for protected execution of Lua
chunks.
The ported version of Lua is 5.1.5.
