Fix arguments of @param, @return etc translations to Python.

For the parameter documentation to be really taken as such, in its entirety,
by Sphinx, it must be indented relative to the :param: tag. Do this by
appending an extra indent after every line of the output and work around the
unnecessary indent of the last line by removing the trailing whitespace.

This required updating the existing tests and removing the expected but not
present any more whitespace from them, but as trailing whitespace in the
documentation is at best insignificant (and at worst harmful) anyhow, this is
not a big price to pay for simpler translator code.

Examples/test-suite/python/doxygen_basic_translate_runme.py

@@ -57,7 +57,7 @@ commentVerifier.check(doxygen_basic_translate.function4.__doc__,
 )
 commentVerifier.check(doxygen_basic_translate.function5.__doc__,
     """
-    This is a post comment. 
+    This is a post comment.
     """
 )
 commentVerifier.check(doxygen_basic_translate.function6.__doc__,