Linux 2.6.32 compat, proc_handler() API change

Linux 2.6.32 compat, proc_handler() API change

As of linux-2.6.32 the 'struct file *filp' argument was dropped from
the proc_handle() prototype.  It was apparently unused _almost_
everywhere in the kernel and this was simply cleanup.

I've added a new SPL_AC_5ARGS_PROC_HANDLER autoconf check for this and
the proper compat macros to correctly define the prototypes and some
helper functions.  It's not pretty but API compat changes rarely are.