Blender Git Loki

GPencil: Correction to rB071ec918f4cd

* correct API convention: in rB071ec918f4cd gp_draw_data drew mulitple data blocks, I added gp_draw_data_all which now calles gp_draw_data multiple times (if needed). This follows our normal convention, e.g. see UI_panel_category_draw_all
* Draw scene data first, users may expect it like this

Points raised by @aligorith, thanks for this!