[PATCH] consolidate do_signal

[PATCH] consolidate do_signal

11 out of our 17 architectures have basically the same code
in arch/../kernel/signal.c:do_signal.  This patch creates a
common function for that bit of code and uses it in the places
it can be.

The 2.5.15 version of this patch builds and runs on i386 and PPC and has
been briefly looked at by the CRIS, PARISC, PPC64 and x86_64 maintainers.

As a bonus, this fixes the "ignore SIGURG" bug for 9 more architectures
(i386 and PPC already were fixed).