Use caller_context_t to stash the cnp and other OSX specific fields

The incoming arguments from the caller layer are represented as vnop_*_args, 
which contains an OSX specific form of the call. These are mapped into the 
zfs_* functions which are typically multi valued in the ZFS case.

The majority of these are identical, except that OSX stores an additional 
struct componentname, which is passed down and through the callers. A lot of 
mapping is used with this in place.

If we adopt the caller_context_t to pass that information through the chain, we 
can harmonise the user interfaces and thus simplify the caller contexts.

Original issue reported on code.google.com by alex.ble...@gmail.com on 23 Dec 2010 at 12:05

fabioz23 / maczfs

Use caller_context_t to stash the cnp and other OSX specific fields #62