Merge branch 'mauro' into docs-mw

Mauro says:

This changeset contains the kernel-doc.py script to replace the verable
kernel-doc originally written in Perl. It replaces the first version and the
second series I sent on the top of it.

I tried to stay as close as possible of the original Perl implementation
on the first patch introducing kernel-doc.py, as it helps to double check
if each function was  properly translated to Python.  This have been
helpful debugging troubles that happened during the conversion.

I worked hard to make it bug-compatible with the original one. Still, its
output has a couple of differences from the original one:

- The tab expansion works better with the Python script. With that, some
  outputs that contain tabs at kernel-doc markups are now different;

- The new script  works better stripping blank lines. So, there are a couple
  of empty new lines that are now stripped with this version;

- There is a buggy logic at kernel-doc to strip empty description and
  return sections. I was not able to replicate the exact behavior. So, I ended
  adding an extra logic to strip empty sections with a different algorithm.

Yet, on my tests, the results are compatible with the venerable script
output for all .. kernel-doc tags found in Documentation/. I double-checked
this by adding support to output the kernel-doc commands when V=1, and
then I ran a diff between kernel-doc.pl and kernel-doc.py for the same
command lines.

The only patch that doesn't belong to this series is a patch dropping
kernel-doc.pl. I opted to keep it for now, as it can help to better
test the new tools.

With such changes, if one wants to build docs with the old script,
all it is needed is to use KERNELDOC parameter, e.g.:

	$ make KERNELDOC=scripts/kernel-doc.pl htmldocs