This restores support for using HTML tag styling of margins on the body.
Reftests post bug still pass for dynamic changes, so does the newly-added
test for body margins and frames that tests the old styling method.
This also removes the reftest list for stylo testing for obvious reasons.
Since these are just interpreted comments, there's 0 impact on actual code.
This removes all lines that match /* vim: set(.*)tw=80: */ with S&R -- there are
a few others scattered around which will be removed manually in a second part.
HTML standardizes proper behavior of colSpan and rowSpan:
The main thing is that getting the .rowSpan and .colSpan IDL properties will now return the actual clamped value that we use.