NOTICE_SIGNAL_HANDLING_CHANGE macro added to the target vector as

NOTICE_SIGNAL_HANDLING_CHANGE macro added to the target vector as
to_notice_signals.

* inferior.h (proc_signal_handling_change): prototype removed.
* infrun.c (NOTICE_SIGNAL_HANDLING_CHANGE): default removed.
(handle_command): now calls target_notice_signals.
* procfs.c (proc_signal_handling_change): renamed to
  procfs_notice_signals.  Now static.  Add prototype.  All callers
  changed.
* target.h (struct target_ops): new field, to_notice_signals.
(target_notice_signals): new macro to cover new field.
* target.c (cleanup_target): default to_notice_signals to ignore.
* corelow.c (core_ops),
exec.c (exec_ops),
inftarg.c (child_ops),
procfs.c (procfs_ops),
remote-adapt.c (adapt-ops),
remote-eb.c (eb_ops),
remote-es1800.c (es1800_ops, es1800_child_ops),
remote-hms.c (hms_ops),
remote-mm.c (mm_ops),
remote-nindy.c (nindy_ops),
remote-st2000.c (st2000_ops),
remote-udi.c (udi_ops),
remote-vx.c (vx_ops, vx_run_ops),
remote.c (remote_ops),
target.c (dummy_target),
xcoffexec.c (exec_ops): added static initializer for
to_notice_signals.
* xm-irix4.h, xm-sysv4.h (NOTICE_SIGNAL_HANDLING_CHANGE): removed.