This patch switches m68k to generic siginfo layout. The custom layout
of m68k's `struct siginfo' had several issues due to not considering
aliasing of members in the union, e.g., _uid32 was at different offsets
in ._kill, ._rt and ._sigchld.

Signed-off-by: Maxim Kuvyrkov
Signed-off-by: Geert Uytterhoeven