Merge branch 'kerneldoc2' into docs-next

Merge branch 'kerneldoc2' into docs-next

So once upon a time I set out to fix the problem reported by Tobin wherein
a literal block within a kerneldoc comment would be corrupted in
processing.  On the way, though, I got annoyed at the way I have to learn
how kernel-doc works from the beginning every time I tear into it.

As a result, seven of the following eight patches just get rid of some dead
code and reorganize the rest - mostly turning the 500-line process_file()
function into something a bit more rational.  Sphinx output is unchanged
after these are applied.  Then, at the end, there's a tweak to stop messing
with literal blocks.

If anybody was unaware that I've not done any serious Perl since the
1990's, they will certainly understand that fact now.