Release 1.0.0b4

This release includes:

• an under-the-hood reworking of functions that makes recursive functions now fully supported;
• VM updates to finally ditch use of a global names dictionary in favour of pushing all values onto the lnames stack, plus a few new instructions;
• boolean solid operations on 3D meshes is improved and now less likely to create bad meshes; and
• a new command-line option for doing a final gamma correction in the window framebuffer render.