1. Move pthread-specific data files from sched/pthread/ to libs/libc/pthread.
2. Remove pthread-specific data functions from syscalls.
3. Implement tls_alloc() and tls_free() with system calls.
4. Reimplement pthread_key_create() and pthread_key_free() using tls_alloc() and tls_free().
5. Reimplement pthread_set_specific() and pthread_get_specicif() using tls_set_value() and tls_get_value()
The new OS interface, sched_get_stackinfo() combines two pthread-specific interfaces into a single generic interface. The existing pthread_get_stackaddr_np() and pthread_get_stacksize_np() are moved from sched/pthread to libs/libc/pthread.
There are two motivations for this change: First, it reduces the number of system calls. Secondly, it adds a common hook that is going to used for a future implementation of TLS.
Squashed commit of the following:
libs/libxx: Fix some confusing in naming. If the directory is called libxx, then the library must be libxx.a (unless perhaps LIBCXX is selected).
libs/: Fix paths in moved library directories.
libs: Brute force move of libc, libnx, and libxx to libs. Cannot yet build it in that configuration.
Huang Qi