glib: Add poppler_document_new_from_bytes
This allows creating a PopplerDocument from data stored in a GBytes.
This is better than poppler_document_new_from_data() since the document will keep a reference to the data, instead of having to make sure manually that the data stays around as long as the document exists. Also poppler_document_new_from_data() is buggy in that it uses int for the data size instead of gsize.