Warn the defined location as deprecation as well as the main message

[Bug #17575]

test/ruby/test_defined.rb

@@ -258,6 +258,23 @@ class TestDefined < Test::Unit::TestCase
     assert_separately([], "assert_nil(defined?(super))")
   end
 
+  def test_respond_to
+    obj = "#{self.class.name}##{__method__}"
+    class << obj
+      def respond_to?(mid)
+        true
+      end
+    end
+    assert_warn(/deprecated method signature.*\n.*respond_to\? is defined here/) do
+      Warning[:deprecated] = true
+      defined?(obj.foo)
+    end
+    assert_warn('') do
+      Warning[:deprecated] = false
+      defined?(obj.foo)
+    end
+  end
+
   class ExampleRespondToMissing
     attr_reader :called
 

vm_method.c

@@ -2503,7 +2503,8 @@ vm_respond_to(rb_execution_context_t *ec, VALUE klass, VALUE obj, ID id, int pri
 		    VALUE path = RARRAY_AREF(location, 0);
 		    VALUE line = RARRAY_AREF(location, 1);
 		    if (!NIL_P(path)) {
-			rb_compile_warn(RSTRING_PTR(path), NUM2INT(line),
+			rb_category_compile_warn(RB_WARN_CATEGORY_DEPRECATED,
+					RSTRING_PTR(path), NUM2INT(line),
 					"respond_to? is defined here");
 		    }
 		}