Re: DLL stuff (BIG patch)

Attached is a rather large patch to 21.0.61 to support DLL loading. I havent done changelog entries yet but this is pretty complete, even a manual. This has the new ellcc compiler program, and a much more complete and well defined interface. Modules are now 100% the same as built-in code, so it should be easy to migrate stuff out of the dumped Emacs into loadable modules. Please apply this (with -E to remove some empty files) and try it out. I think this works pretty well. No doubt I will have to polish things a little but I would really like to see this stuff in the tree sooner rather than later so that people can get used to the idea, and we can start thinking about which parts of the currently dumped Emacs we want to turn into modules.