Fix infinite loop when accessing circular constants from inline assembly.

libsolidity/ast/ASTUtils.h

@@ -28,4 +28,7 @@ class VariableDeclaration;
 /// Returns nullptr if an identifier in the chain is not referencing a constant variable declaration.
 VariableDeclaration const* rootConstVariableDeclaration(VariableDeclaration const& _varDecl);
 
+/// Returns true if the constant variable declaration is recursive.
+bool isConstantVariableRecursive(VariableDeclaration const& _varDecl);
+
 }