Item about pdf-annot list buffer
Use pos arg when adding text annotations.

* lisp/pdf-annot.el (pdf-annot-add-text-annotation): Give x,y as
  position argument, allowing for posnp or plain cons.
  (pdf-annot-add-text-annotation): Change arguments of above function.
  (pdf-annot-mouse-add-text-annotation): Change arguments of above function.
Fixed typo.
Use proper values when signaling an error.