SQL Search functional improvements proposal

Here are a series of functional improvements which I have been thinking about for trip_search: comments on these would be welcome:

1. Make previously entered search values appear in the advanced search form, or the simple search form, depending on which one was used to enter the search (it used to do this and it somehow got broken)
2. Provide a means for handling stopwords for different languages (using the PO file for example?)
3. provide an externally callable trip_search function, for example allowing it be called from a "page not found" page to direct the user to possible matches
4. investigate possibilities of using MySQL ranking to improve search results
5. if possible, find some way of making sure that results get returned properly even when the word being searched for is up against some HTML formatting: for example if you search for "New features", and you have a node which contains this: <h4>New features</h4>, then that node will not be returned because "features" is stuck up against the heading statement