Add a -tlex option to debug the lexer.

Also, rename the rules in parser.mly now that their appear in the manual.
This renaming work is in progress though.

not compile them is (well, was) the default...).

also, during pretty-printing, remove the type in the constant definition
(e.g., "const x = 42;" instead of "const x = 42:int;"), except if it is an abstract
constant of course