* pre-R13: finish remaining entities and the blocks.
* PROXY subentities, PROXY_ENTITY
* CELLSTYLEMAP TABLE_Cell struct
* MULTILEADER: broken Leader_Line's/Points
* DIMSTYLE_CONTROL: one R2000+ RC missing
* r2010+ some AEC (Autodesk Architectural Desktop) object invalid EED's.
* Enabled, but untested: FIELDLIST, AcDbField, TABLECONTENT, TABLEGEOMETRY,
  GEODATA, LONG_TRANSACTION, OBJECT_PTR
* Unhandled (fields spec'ed but broken/untested): MATERIAL, CELLSTYLEMAP,
  MULTILEADER, PROXY, PROXY_ENTITY, PLOTSETTINGS, LIGHT, SUN,
  GEOPOSITIONMARKER, EXTRUDEDSURFACE
* Unhandled (i.e. passed through, no DXF and fields): TABLESTYLE,
  DBCOLOR, VBA_PROJECT, DIMASSOC, LIGHTLIST, LEADEROBJECTCONTEXTDATA,
  ACDBSECTIONVIEWSTYLE, ACDBDETAILVIEWSTYLE,
  ACDBASSOCNETWORK, ACDBASSOC2DCONSTRAINTGROUP,
  ACDBASSOCGEOMDEPENDENCY, ACDB_LEADEROBJECTCONTEXTDATA_CLASS,
  NPOCOLLECTION, EXACXREFPANELOBJECT, ARCALIGNEDTEXT (2000+),
  UNDERLAYDEFINITION (2 strings), OBJECTCONTEXTDATA, RTEXT,
  AcDbAnnotScaleObjectContextData
* add test coverage - i.e. an extended example_2018.dwg with all types,
  for the following missing entities:
  BODY CAMERA DIMENSION_ANG3PT DIMENSION_DIAMETER
  DIMENSION_RADIUS DUMMY SURFACE
  POSITIONMARKER IMAGE LEADER LONG_TRANSACTION MINSERT
  OLE2FRAME OLEFRAME POLYLINE_2D POLYLINE_MESH
  PROXY_ENTITY PROXY_LWPOLYLINE SHAPE
  TOLERANCE VERTEX_2D VERTEX_MESH HELIX
* likewise for the following missing objects:
  ARCALIGNEDTEXT ASSOC2DCONSTRAINTGROUP ASSOCGEOMDEPENDENCY
  ASSOCNETWORK CELLSTYLEMAP CSACDOCUMENTOPTIONS DBCOLOR DETAILVIEWSTYLE
  DIMASSOC EXACXREFPANELOBJECT GEODATA IDBUFFER IMAGEDEF
  IMAGEDEF_REACTOR LAYER_INDEX LEADEROBJECTCONTEXTDATA LIGHTLIST
  NPOCOLLECTION OBJECTCONTEXTDATA OBJECT_PTR PLOTSETTINGS PROXY_OBJECT
  RASTERVARIABLES SECTIONVIEWSTYLE SORTENTSTABLE SPATIAL_FILTER
  SPATIAL_INDEX SUN TABLECONTENT TABLEGEOMETRY UCS
  VBA_PROJECT VIEW VPORT_ENTITY_CONTROL VPORT_ENTITY_HEADER
* check-dxf: DXFIN coverage for all generated dxfs. some objects even crash acad:
  VERTEX_3D, MLINE.
* DXFIN errors:
  Drawing_2007-18: XRECORD starting at line 5318: Could not set the Color dictionary:
  *2010: Updating handle seed. Invalid or incomplete DXF input
  *2007: XRECORD read error
  *2004: PolyLine3D crashes at AcDb3dPolylineVertex
  example_2000: REGION starting at line 2506: Xdata wasn't read
  Drawing_2000_min: crash at AcDbLine

* convert XRECORD xdata linked-list ResBuf to array of eed[],
  same structure as common EED.
* link VBA_PROJECT object to its section, and vice versa
* merge decode_r2007 with the 2004 decoder. It is almost the same, just
  the sections have multiple pages. Only for this version. 2010+ uses
  the 2004 format.
* encode for 2004+: move the local structs to the dwg, as union?
* finish binary DXF (easy). cross-check via: filedia 0, dxfout => Binary
* add DXF reading (medium)
* finish GeoJSON http://geojson.org/geojson-spec.html
* maybe dwgfilter, as from the osmctools, with keep and drop rules.
* add getopt_long() for position independent options
* check osm tools https://gitlab.com/osm-c-tools/osmctools how
  they could import GIS data easier.
  Check OpenStreetMap XML and PBF formats.
* add one of the easy OGR formats: gml, gpx. See the xmlsuite which does it also.
  See https://wiki.openstreetmap.org/wiki/Dxf2gpx
  https://grass.osgeo.org/grass74/manuals/v.in.dxf.html and dwg (teigha and opencad)
* add geomutils to tesselate curves (e.g. GeomJSON),
  and to transform OCS/UCS objects when being displayed (e.g. svg, ps).
  add API funcs to find table elements (layer, ltype).
* ACIS: implement parsing of SAT file version 2 (ShapeManager, forked from ACIS 7.0)
* map DWG constraints to FreeCAD and SolveSpace constraints
  https://www.freecadweb.org/wiki/Sketcher_Workbench#Sketcher_Constraints
* check valabind vapi files to generate more and better bindings
  (e.g. radare2-bindings). c++, rust, go, node, java, perl, ruby, php,
  autolisp (via ARX).
  Did so, I dislike it. Too much work, valabind crashes and requires glib and gobject.
  See the work/vapi branch.
* add some UI to inspect the DWG internal structs (dwgiview), and maybe a viewer (dwgview).
  Started with perl-tk

* fix the remaining leaks (xdata?, unicode texts).
* finish documentation of the API functions, refman.
* add the basic DWG layout and API to the docs.
* publish manual and link to doxygen refman API
* add more defaults when encoding from older to newer versions.
* add fuzzing and solver-based test generation (bits)
* check testsuite errors when cross-compiled under wine.
  latest wine needs a new WINEARCH env var.
* check for a waiver/copyright assignment from
  Alex Papazoglou <papazoga> for his reed-solomon code (yet unused).
  Otherwise use rscode-1.3 by Henry Minsky <hqm@alum.mit.edu> which is GPLv3.
