Spec 'Signal.trap ignores the signal when passed nil' OK for rx19:
  - extract Signal.trap from kernel/common/signal.rb to
    kernel/common/signal18.rb;
  - create a new file kernel/common/signal19.rb with new version for
    Signal.trap:
      - in case stattement, add a new +when nil+ statetement which
        set +prc+ to +nil+;
      - in +when "IGNORE", "SIG_IGN"+ statement, +prc+ is set to
        "IGNORE" string;
      - in Rubinius.watch_signal, replace +prc.nil?+ with
        +prc.nil? || prc == 'IGNORE'+;
      - return statements now return +nil+ when +old+ is false
        instead of "IGNORE";
  - modify kernel/common/load_order*.
kernel/common/signal19.rb:
  modify first Rubinius.watch_signal as second in previous commit.

spec/tags/19/ruby/core/signal/trap_tags.txt:
  remove fail tag on core/signal/trap spec.
Merge branch 'sigtrap19' of github.com:sdaubert/rubinius into sigtrap19