This patch pulls together the compat_sigevent structs.  It also
consolidates the copying of these structures into the kernel.

The only part of the second union in sigevent that the kernel looks at
currently is the _tid, so that is the only bit we copy.

This patch depends on my previous two patches "add and use
COMPAT_SIGEV_PAD_SIZE" and "Consolidate the last compat sigvals".
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>