the getfiles command now returns nil if the given directory doesn't exist
added download.lua and documented recent changes
implemented a geturl function so Lua scripts can download a file from a given URL
updated makefile-mac to wx 3.2.7
removed the AGL framework from makefile-mac (no longer needed)
added disable-arttango to the configure options for building wxWidgets on macOS (avoids ugly icons in file panel)
removed the AGL framework from makefile-mac (no longer needed)
Merge branch 'master' of ssh://git.code.sf.net/p/golly/code into master