* Simplify EINTR/ECANCEL error handling
1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx
* Unify the void cast usage
1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro
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.
