ni_nitdoc: Get all inherited method in a class

Signed-off-by: Stefan Lage <lagestfan@gmail.com>
ni_nitdoc: Check if a mclass has a mmodule

Signed-off-by: Stefan Lage <lagestfan@gmail.com>
ni_nitdoc: Associate a mpropdef to its mmethod

Signed-off-by: Stefan Lage <lagestfan@gmail.com>
ni_nitdoc: Associate mpropdef to its mmethod before process each mclass