highlight section on section edit button mouseover

Ignore-this: 128d5873729a0a00558465b45d5d9f58

Some people seem to have problems to see which section will be edited when
using a section editing button. This patch adds a litle bit JavaScript magic
to highlight the edited section to be, when hovering over a section button.

darcs-hash:20090214161135-7ad00-59db7d9185784ba1fec2f2c2da30c6e64ae1ccc3.gz