Fixed PR11955 by updating the signal tapset.

Fixed PR11955 by updating the signal tapset.

* tapset/linux/signal.stp (signal.send): Now uses the 'signal_generate'
  tracepoint where available. Deprecated the 'send2queue' variable.
  (signal.send.return): Deprecated.
  (signal.handle): Now uses the 'signal_deliver' tracepoint where
  available. Deprecated the 'oldset_addr' and 'regs' variables.
  (signal.handle.return): Deprecated.
* testsuite/buildok/signal-detailed.stp: Updated with 'signal.send',
  'signal.send.return', and 'signal.handle.return' deprecations.
* NEWS: Added deprecation notes.