The compiler should be more or less functional by now, just need some
cleaning and improvement to generate the real binary...

This class isn't so much flexible, but makes code cleaner and easier to
read. All if/then/else template are also replaced by the use of this
class.

Prepare the automata translation, with a dedicated context for each.
Add partial expression translation (some assignments, binary operators,
constants, variable definition...)

Some dirty stuff was added to avoid an issue with an LLVM template in
PassManager, API seems broken but no useful information is available to
understand why...

All binary operators have the same precedance due to a "feature" of yacc
that makes difficult to write something better without some
duplications.

Language is now fully recognized, and AST is generated as expected.

Add many node types and improve bison/flex description.
Now the recognized lnguage is quite similar to the "auto" language, but
not complete.