Update Makefile to allow for paths with spaces in them

[Piroshky]

When I tried to use the Makefile to download the wiki sources it ended up deleting the
directory it was called from, due to the Makefile not being able to handle paths with
spaces in them.

The fix is to wrap the variables that hold the path in quotes when they are being passed
as arguments to commands.

[filiparag]

Thanks for opening the pull request. I am sorry for not replying earlier.

I noticed that you simplified declaration of MKFILEABS variable to use MAKEFILE_LIST. Unfortunately, FreeBSD's make impelentation desn't support it, so I can't accept that change, as it would break compatibility. The rest of changes are good and can be merged to the upstream.

I revised spacing fixes you provided so it follows cat's 8 character tabs. Hope you don't mind.