MFC r331329: Fix kernel memory disclosure in ibcs2_getdents

MFC r331329: Fix kernel memory disclosure in ibcs2_getdents

ibcs2_getdents() copies a dirent structure to userland.  The ibcs2
dirent structure contains a 2 byte pad element.  This element is never
initialized, but copied to userland none-the-less.

Note that ibcs2 has not built on HEAD since r302095.

Submitted by:	Domagoj Stolfa <ds815@cam.ac.uk>
Reported by:	Ilja Van Sprundel <ivansprundel@ioactive.com>
Security:	Kernel memory disclosure (803)
Sponsored by:	The FreeBSD Foundation