document: ev_mapping_list_get_all

Implements a function that returns all EvMappings
at a certain point. Needed for annotations
(especially text markups), whose bounding boxes
might overlap.
libdocument: adding method is_xy_in_annotation

Added the method is_xy_in_annotation to the
interface of document-annotations. It intends to
check if a point (x,y) is inside the annotation's
quadrilaterals (and not its bounding box, which
can be checked using the EvMapping).
pdf: implemented is_xy_in_annotation

Implements the function that checks whether a point
(x,y) is inside an annotation.
libview: checking if point is inside annotation

Added a step to check if a point is inside an
annotation. In case it is foud to be inside the
bounding box, view asks the document if it is
actually inside the annotations, since the
quadrilaterals might not comprise the whole are of
the bounding box. Only then it become selectable.