Fix autodoc strings generated in Python builtin case and the test.

Use the proper AUTODOC_METHOD for autodoc strings generation when using
"-builtin", there is no reason to use AUTODOC_FUNC here when AUTODOC_METHOD is
used by default (i.e. without "-builtin").

This allows to (almost) stop differentiating between the two cases in the
autodoc unit test, allowing to simplify it significantly.

Also fix this test to pass after the recent changes removing docstring
indentation in the generated code.
Remove trailing space from one of Doxygen tests.

This resulted in a warning (treated as error) from pep8 1.5.7 when running
Doxygen test suite for Python.
Remove any whitespace before ignored Doxygen commands.

This is done mainly to avoid problems with trailing whitespace in the
generated Python code as this provokes pep8 problems, but is also, arguably,
more logical, as if a command which is on its own on a line is ignored, we
shouldn't leave any whitespace neither (and perhaps should even suppress the
line entirely, in fact).