[patch] support syscall.sigaltstack for all archs

[Frank Ch. Eigler]

Lai Jiangshan <laijs@cn.fujitsu.com> writes:

> [...]order to offer probe for all archs, I added
> syscall.sigaltstack(by probe kernel function do_sigaltstack) in
> syscalls2.stp and deleted syscall.sigaltstack in i686/syscalls.stp,
> ppc64/syscalls.stp and x86_64/syscalls.stp.

This makes good sense.  If you can find/create a testsuite item that
checks this on a few hosts, please feel free to commit.

- FChE