Document the return type when translating Doxygen @return to Python.

In addition to translating the comment itself, also document the type of the
object returned. This is consistent with generating not only :param: but also
:type: for the parameters documented using @param.

Examples/test-suite/python/doxygen_basic_translate_runme.py

@@ -13,6 +13,7 @@ commentVerifier.check(doxygen_basic_translate.function.__doc__,
 
     Author: Some author
 
+    :rtype: int
     :return: Some number
 
     See also: function2
@@ -86,6 +87,7 @@ commentVerifier.check(doxygen_basic_translate.Atan2.__doc__,
     :param y: Vertical coordinate.
     :type x: float
     :param x: Horizontal coordinate.
+    :rtype: float
     :return: Arc tangent of ``y/x``.
     """
 )

Examples/test-suite/python/doxygen_translate_all_tags_runme.py

@@ -263,10 +263,13 @@ r"""
 
     Another remarks section
 
+    :rtype: int
     :return: Whatever
 
+    :rtype: int
     :return: it
 
+    :rtype: int
     :return: may return
 
     """)

Examples/test-suite/python/doxygen_translate_runme.py

@@ -99,10 +99,13 @@ r"""
 
     Another remarks section
 
+    :rtype: int
     :return: Whatever
 
+    :rtype: int
     :return: it
 
+    :rtype: int
     :return: may return
 
     See also: someOtherMethod