Construct an XDOC tree for a source link directive @(srclink ...).
Macro:
(defmacro @srclink (&rest trees) (list '@srclink-fn (cons 'list trees)))
Function:
(defun @srclink-fn (trees) (declare (xargs :guard (tree-listp trees))) (make-tree-dir/&& :@srclink trees))
Theorem:
(defthm stringp-of-@srclink (equal (treep (@srclink-fn trees)) (tree-listp trees)))