* 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
many locations: Change occurences of open() followed by file_detach() to file_open(). Change most non-controversion calls to open() to nx_open().
fs/inode/fs_fileopen.c: Flesh out file_open() with some interim, placeholder logic.
fs/inode/fs_fileopen.c: Add a framework for a file_open() implementation (no real logic in place yet).
fs/vfs/fs_open.c: Add nx_open() which is the same as open() except that it does not create a cancellation point nor does it modify the errno variable.
As a policy, all internal OS implementations must use "detached" files which are valid in any context and do not depend on the validity of a file descriptor at any point in time. This commit converts the usage of file descriptors to detached files throughout the local socket implementation.
Squashed commit of the following:
net/local: Finish change to eliminate use of file descriptors.
net/local: A little more of the conversion.
net/local: Beginning of chnages to eliminate use of file descriptors in the local socket implementeation. poll() will be a problem.
