[v3] doxygen updates

[Phil Edwards]

> INPUT      = \
[...]
>            include/i686-pc-linux-gnu/bits

This seems wrong.  Granted that few if any people will be generating the docs
from scratch on any other build system :-),  but this still seems inflexible.


>   * docs/doxygen/filter: Remove.
>   * docs/doxygen/filter.sed: Remove.

Why?  This is what translated the uglified names in the source to more
readable names (without abbreviations and tons of underscores) in the output.
I looked for some other part that was now doing this, but can't find it.


-- 
America may be unique in being a country which has leapt
from barbarism to decadence without touching civilization.
  - John O'Hara