New file - asm-generic/signal.h.  Contains declarations of
__sighandler_t, __sigrestore_t, SIG_DFL, SIG_IGN, SIG_ERR and default
definitions of SIG_BLOCK, SIG_UNBLOCK and SIG_SETMASK.

asm-*/signal.h switched to including it.  The only exception is
asm-parisc/signal.h that wants its own declaration of __sighandler_t;
that one is left as-is.

asm-ppc64/signal.h required one more thing - unlike everybody else it
used __sigrestorer_t instead of usual __sigrestore_t.  PPC64 switched to
common spelling.

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>