Remove executable permissions from all files.

None of the files in this repo can actually be executed by the operating system, so it doesn't make sense for them to have executable permissions.  This changeset removes those permissions.

I notice there is a commit with the message "Mode changed to 0755 due to copy on NTFS drive", which is probably how they got there in the first place (although why that change was ever committed and pushed, I can't imagine.)