Construct an XDOC tree for an evaluation directive @(`...`).
Macro:
(defmacro |@''| (&rest trees) (list '|@''-FN| (cons 'list trees)))
Function:
(defun |@``-FN| (trees) (declare (xargs :guard (tree-listp trees))) (make-tree-dir/&& :|@``| trees))
Theorem:
(defthm |STRINGP-OF-@``| (equal (treep (|@``-FN| trees)) (tree-listp trees)))