Fix source files with executable bit

[hoffie]

Multiple source files somehow have the executable flag set.
Something like find src/ -type f -exec chmod -x {} \; should to the trick.

Originally posted by @vimpostor in #1649 (comment)

[gilgongo]

Wonder why? I've noticed +x happening on files transferred from Windows clients to rsync mounts in some circumstances, but that wouldn't seem to apply to git.

[vimpostor]

The files did have the execute flag since the very first commit from 15 years ago.
Probably some Ntfs in Linux scenario that caused this.