Update size of PDF files
8.3 is no longer supported, so move the documentation links to the archive

We keep them around like all other old documentation versions of course, but we
move them away from the main page.
Drop windows CHM file for documentation

These files haven't been updated for years (8.3.0 and 8.4.0 respectively),
and are hard/impossible to automate the build of. And clearly not many people
are actually using them, since we've had no complaints about the versions
that are there being old.