Squashed 'lectures/' changes from 2b1085b..521754d ...

521754d • Added an adjustment to ensure that there is always a space before the note number. Required when we have to put a % at the end of the previous line to suppress a line break that would otherwise appear in the presentation slides. (Note numbers appearing at the start of a line will be slightly indented.)

git-subtree-dir: lectures
git-subtree-split: 521754d

Squashed 'lectures/' content from commit 2b1085b ...

git-subtree-dir: lectures
git-subtree-split: 2b1085b