Added tag ahven-2.8 for changeset 275a2332c0bb
Update README.md for 2.8.

Update the Debian package installation section (patch
from Nicolas Boulenguez) and remove the obsolete
documentation links.
Update NEWS.txt for 2.8
Link the shared library with LDFLAGS.

Comfignat transmits them to gprbuild via -largs, which affects
executables but not libraries.

From Nicolas Boulenguez, thanks!
Handle JAWSII envvar with and without backlash at the end.
Add intro text for Ahven.XML_Runner package doc.
Increase soversion to 28.
Increase version to 2.8.
Update copyright year to 2020.
Change .build.yml sources to Mercurial repository.
Fix git repo url.
API doc wording fixes.

Procedure Run variant with Test_Name parameter will surely
call all tests with same name (not just might).
Add build.sr.ht config. Remove bitbucket build config.

Change the build configuration to use Sourcehut's
build infrastucture.
Fix command example formatting in README.md.
Fix README.rst to README.md in README.md.
Use lowercase letters in hg repo url.
Rename README.rst to README.md.

Sourcehut renders only Markdown READMEs.
Mercurial repository now at sourcehut.

New address for hg repo is https://hg.sr.ht/~tkoskine/Ahven
Update Janus/Ada build script modifications to documentation.
Reorganize Janus/Ada build scripts.

Reduce the build script amount and keep only
 janusada\prepare.bat
 and janusada\build.bat
scripts.

prepare.bat is run as the first thing on clean workspace to
setup the project files and build.bat will build the actual source code.
Next