Two modifications:
1. The addition of 2013 to the copyright year range for every file;
2. The use of a single year range, instead of potentially multiple
year ranges, as approved by the FSF.
* lib/gdb.exp (can_single_step_to_signal_handler): New.
* gdb.base/kill-after-signal.exp: Call it. Skip if target doesn't
support single step to signal handler.
