htmlreport: fix syntax highlighting broken in ca4a0af840f45107ce33d902bd4d77d5af09aedf.
htmlreport: remove black background, make the report a bit more space efficient.
Merge pull request #333 from matthiaskrgr/htmlreport_fix_colors

htmlreport: fix syntax highlighting broken in ca4a0af840f45107ce33d902bd4d77d5af09aedf