add abstract of content as title attribute to node links

this is done in the (new) forum.module: when you hover over a link in the forum block ("Most active forum topics"), you see the first 100 chars of the topic content as a tooltip*. i really like this, as it offers a quick way of seeing more about this topic (and assessing if it's worth viewing it) without having to actually view it.

and suggest to add this functionality to every link that goes to a node with content (ie. blog links, most popular links, etc).

* at least in ie and mozilla - opera apparently (said dries) doesnt show <a title> tooltips. i'm not so sure about this (opera) - if it isn't shown as tooltip, wasn't it shown in the status bar? wasn't there an option to set this? anyway, the spec says: The title attribute may be set for both A and LINK to add information about the nature of a link. This information may be spoken by a user agent, rendered as a tool tip, cause a change in cursor image, etc. so, in a standard compliant browser, it should be viewable somehow in any case.