The generation script used different flags from the Makefile.

The back_link points to the hash table and should use a hash_index.

Converted LaTeX sources to Sphinx
- Changed from PDF/paper compendium to git/sphinx
- Updated instructions for gitlab
- Changed PNGs to Graphviz files

Updated the lab source code
- Now uses doxygen integrated with the documentation
- Resolved many issues with instructions and code
  not being in sync

Documentation is built by GitLab CI using docker.

Included flex/bison/gcc/x86-asm documentation for convenience.

CI/CD runs the labs and creates a file called testsuite.html to get
a good status of the repository with a clean build (to check student
work easier).