Modified webbugs filter to create a comment around the offending

Modified webbugs filter to create a comment around the offending
image instead of removing it entirely.

Adjusted regex to only match if there's at least one whitespace
before the width and height attributes. Makes it more likely that
they are indeed attributes, and not part of the value of another attribute.
Solves BR 1035587.

Thanks to Martin Thomas for diagnosing the cause of the problem.