Merge script principal implementations into one class.
Should reduce footprint, speed up calls to caps a little bit, and fixes several memory leaks.
Also fixes bugs 211174 and 211263
r=jst@netscape.comsr=bzbarsky@mit.edumoa=mstoltz@netscape.com (he looked at an earlier patch and said it looked fine, and will do a retroactive review when he returns from vacation as well)
git-svn-id: svn://10.0.0.236/trunk@145137 18797224-902f-48f8-a5cc-f745e15eee43
cd46cbbaad