make use of C++ = default constructor declarations as well as more non-static member initialization syntax.

libsolidity/ast/ASTAnnotations.h

@@ -46,7 +46,7 @@ using TypePointer = std::shared_ptr<Type const>;
 
 struct ASTAnnotation
 {
-	virtual ~ASTAnnotation() {}
+	virtual ~ASTAnnotation() = default;
 };
 
 struct DocTag
@@ -57,7 +57,7 @@ struct DocTag
 
 struct DocumentedAnnotation
 {
-	virtual ~DocumentedAnnotation() {}
+	virtual ~DocumentedAnnotation() = default;
 	/// Mapping docstring tag name -> content.
 	std::multimap<std::string, DocTag> docTags;
 };

libsolidity/ast/Types.h

@@ -601,7 +601,6 @@ private:
 class BoolType: public Type
 {
 public:
-	BoolType() {}
 	Category category() const override { return Category::Bool; }
 	std::string richIdentifier() const override { return "t_bool"; }
 	TypeResult unaryOperatorResult(Token _operator) const override;