Change SyntaxChecker prototype

No choice, it must have a SyntaxReport as an argument. Otherwise piggybacking on
the syntax processor doesn't work, since its validate() method expects that type
of argument. Same goes for .checkValue().

Tests have their limitations... If only spying on final classes were easy.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
Modify base abstract tests

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>