The name var was getting clobbered in the initial for-in loop, so the
second loop would never be entered.

Closes #1691

Also adds parameters to a range's clear event.

Issue #1678
Issue #1679

Issue #1668

Use it to prevent some unneeded state computation.

Issue #1653

Move hinting functions into it.

Since the addon is called merge, not diff.

Apparenly Firefox still hasn't caught up on the unprefixed version.

+ a few other fixes

Issue #1625

Issue #1625

Work around percentage width rounding problems.

Also makes sure that no two hinting dialogs can be active at the
same time.

Issue #1619

Use it to make xml-fold more robust, and matchbrackets much faster.