test_defer: avoid declaring TestDeferUsage class on Ruby 1.9.

Since the only test present in the class would be skipped under Ruby 1.9,
avoid declaring the whole class, leaving the file empty.

This change is necessary for the testsuite to pass green when test-unit-2
is installed, as empty Test::Unit::TestCase-derived classes produce errors.

Signed-off-by: Aman Gupta <aman@tmm1.net>

tests/test_defer.rb

@@ -28,20 +28,22 @@
 require 'eventmachine'
 require 'test/unit'
 
-class TestDeferUsage < Test::Unit::TestCase
+unless RUBY_VERSION >= '1.9.0'
+  class TestDeferUsage < Test::Unit::TestCase
 
-  def test_defers
-    n = 0
-    n_times = 20
-    EM.run {
-      n_times.times {
-        work_proc = proc { n += 1 }
-        callback = proc { EM.stop if n == n_times }
-        EM.defer work_proc, callback
+    def test_defers
+      n = 0
+      n_times = 20
+      EM.run {
+        n_times.times {
+          work_proc = proc { n += 1 }
+          callback = proc { EM.stop if n == n_times }
+          EM.defer work_proc, callback
+        }
       }
-    }
-    assert_equal( n, n_times )
-  end unless RUBY_VERSION >= '1.9.0'
+      assert_equal( n, n_times )
+    end
 
+  end
 end