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.

include/sys/types.h

@@ -19,6 +19,7 @@ extern "C" {
 #include <linux/kallsyms_compat.h>
 #include <linux/mutex_compat.h>
 #include <linux/module_compat.h>
+#include <linux/sysctl_compat.h>
 
 #ifndef HAVE_UINTPTR_T
 typedef unsigned long			uintptr_t;