parser: generating the IR for the NName and NDeclarations types.
backend: typo.
utils: added the Problems class.

This class encapsulates an std::vector<Problem> with some convenient methods on
top of it.
Show all the errors at once.

Do not stop when syntax errors have been found, but try to evaluate the
resulting code to try to get semantic errors as well.
backend: added the `character` type.