Since the only caller of page_unprotect() which might cause it to
need to call cpu_resume_from_signal() is handle_cpu_signal() in
the user-mode code, push the longjump handling out to that function.
Since this is the only caller of cpu_resume_from_signal() which
passes a non-NULL puc argument, split the non-NULL handling into
a new cpu_exit_tb_from_sighandler() function. This allows us
to merge the softmmu and usermode implementations of the
cpu_resume_from_signal() function, which are now identical.
Backports commit f213e72f2356b77768b9cb73814a3b26ad5a0099 from qemu
Remove them from the sundry exec-all.h header, since they are only used by
the TCG runtime in exec.c and user-exec.c.
Backports commit 1652b974766401743879d78f796f44b8929b0787 from qemu
