Adjust code block style

Smaller font; restore normal line height.
Reduce the text size of inline code, too

Tone down the difference.
Add extra margin above headings
Remove <div> quines around syntax highlighting blocks
Set white-space: pre; for code blocks

This protects Objective-C method notation against ugly line breaks
(after the - or + in '-someMethod:').
Post: "Subclassing Delegates"
Copy footnotes inline with JavaScript; display with CSS

Footnotes triggered by links near the right side of the page can clip
off the edge. Need to fix this.