Suppress warnings in two tests

Failed build in #70.
Pre-3.0 versions of Ruby didn't support pattern matching, and power_assert warned.

Author: olleolleolle

test/test_timeout.rb

@@ -250,7 +250,7 @@ def test_fork
 end
 
 deftest_threadgroup
-assert_separately(%w[-rtimeout],<<-'end;')
+assert_separately(%w[-W0-rtimeout],<<-'end;')
  tg = ThreadGroup.new
  thr = Thread.new do
  tg.add(Thread.current)
@@ -263,7 +263,7 @@ def test_threadgroup
 
 # https://github.com/ruby/timeout/issues/24
 deftest_handling_enclosed_threadgroup
-assert_separately(%w[-rtimeout],<<-'end;')
+assert_separately(%w[-W0-rtimeout],<<-'end;')
  Thread.new {
  t = Thread.current
  group = ThreadGroup.new