Create BaseClassSymbol using its factory method.
Add missing #include <algorithm>.
Add ValueKind and ExpressionAST::resolve(ty, kind).

The method resolve() is used to publish the type
and the kind of an expression.
Remove support for parsing a sequence of string literals.

We will do it properly in the preprocessing phase.
Resolve the type of the Literal expressions.
Make the typechecker optional and add rules to check primary exprs.
Check the symbol parsed by the name(yyast,scope) rule.
Resolve the type of names type specifiers.