doc/main.tex: Precise that only unnamed semantic values can be referred using positional identifiers.

lowercase letter.

plus a comment on compatibility with ocamlyacc
when there are end-of-stream conflicts.

Not useful in practice; preparation for further changes.

Documentation update.

Defined the type [stack] as an abbreviation for [element stream].

This guarantees the absence of name clashes.

Added links to CompCert's github repository.

Spell-checking.