Fix checksum of 'OK' smurffile

Caused by a90ca902edf :)
MDLSITE-3422 ci: Various improvement to smurf files

This commit solves/improves these:

XML:
- Added "numerrors" and "numwarnings" attributes to every check.
- Added grand totals for the above to the <smurf> element.

HTML:
- Show the new totals from the XML.
- Group problems by file, clearly separanting them.
- Difference errors (red) and warnings (orange).
- Cleverer handling of line numbers.
- Dim the "details" section to make it less prominent.