Add selection pins size setting for polygons, rectangles etc.

When using PDFLayoutView, after shape annotation (circle, polygon, rectangle, polyline, line) is selected, selection pins appear (see attached image) 
These pins are too small and its quite hard to tap them. It would be great to have a g_annot_pin_size parameter in Global object so I can increase the size of selection pins.
See PDFLayoutView.m_annot_op_resize, currently, pin size is hardcoded (4dp)