English language proofreading up to 12.1 (including)

I'm done up to 12.1, this is probably the last pull request for the year, as I'll be away at 31c3, I'll continue in January.
Original stated "There are no shadow space requirement' and the new change is 'There are is shadow space requirement', but could be 'There are shadow space requirements'  (I left the markdown for syntax out, but that should be retained.)