Aggiorna Makefile.
Add appunti-concorrenza.md.
Update .gitignore.
DOCS: add stub of class diagram in Metapost language.
Update .gitignore.
DOCS: add command \code to LaTeX source.
DOCS: add report stub and partial section subdivision.
DOCS: add use of package algpseudocode.
DOCS: add new command \strong to LaTeX source.
DOCS: add brief description of concurrent classes.
DOCS: add description of used threads.
DOCS: add join() to list of concurrent constructs in use.
DOCS: update Makefile.