[Bug #19471] `Regexp.compile` should handle keyword arguments

As well as `Regexp.new`, it should pass keyword arguments to the
`Regexp#initialize` method.

re.c

@@ -4688,7 +4688,7 @@ Init_Regexp(void)
 
     rb_cRegexp = rb_define_class("Regexp", rb_cObject);
     rb_define_alloc_func(rb_cRegexp, rb_reg_s_alloc);
-    rb_define_singleton_method(rb_cRegexp, "compile", rb_class_new_instance, -1);
+    rb_define_singleton_method(rb_cRegexp, "compile", rb_class_new_instance_pass_kw, -1);
     rb_define_singleton_method(rb_cRegexp, "quote", rb_reg_s_quote, 1);
     rb_define_singleton_method(rb_cRegexp, "escape", rb_reg_s_quote, 1);
     rb_define_singleton_method(rb_cRegexp, "union", rb_reg_s_union_m, -2);

test/ruby/test_regexp.rb

@@ -700,6 +700,11 @@ class TestRegexp < Test::Unit::TestCase
       assert_equal(//n, Regexp.new("", Regexp::NOENCODING, timeout: 1))
 
       assert_equal(arg_encoding_none, Regexp.new("", Regexp::NOENCODING).options)
+
+      assert_nil(Regexp.new("").timeout)
+      assert_equal(1.0, Regexp.new("", timeout: 1.0).timeout)
+      assert_nil(Regexp.compile("").timeout)
+      assert_equal(1.0, Regexp.compile("", timeout: 1.0).timeout)
     end
 
     assert_raise(RegexpError) { Regexp.new(")(") }