I didn't consider that all newlines in the pre block will be printed and we
thus shouldn't wrap html that has it's tags on separate lines (i.e. contains
superfluous newlines) - wrapping in a div less accurately represents
org-html-export but it provides the same information and gives us more freedom
in the return value of HighlightCodeBlock as well as allowing us to keep the
html tags on new lines (consistency).
97fe8b7850