Better versioning for LaTeXML 0.8.4

[matteosecli]

Here I got it wrong:

latexml-packaging/debian/changelog

Line 1 in 462fb26

latexml (0.8.3) unstable; urgency=medium

it should have been 0.8.3-1.

So, for the next release:

• Fix the version in the changelog.
• Always use a scheme upstream_version-debian_revison for the debian_version.
• Update the corresponding recipes in the PPAs. The daily one should be ok as it is, but the stable one should use a versioning 0.8.4-debrevision+masterrevision.