We need to consider the implications of wide-strings passed to things like 
stoppers and such. Do we need to convert them to UTF8? This is already done for 
a few methods, and the docs mark these as wide-string aware.

Need to implement functions:

spelling and synonym modification methods in WriteableDatabase.

Pike Glue Classes we need to write:

Xapian::ExpandDeciderAnd	ExpandDecider subclass which rejects terms using two ExpandDeciders
	(note: a direct implementation is not strictly necessary, as you could just pass a function 
          that handled this.)
Xapian::ExpandDeciderFilterTerms	ExpandDecider subclass which rejects terms in a specified list
	(note: a direct implementation is not strictly necessary, as you could just pass a function 
          that handled this.)

Xapian::ErrorHandler	Decide if a Xapian::Error exception should be ignored
Xapian::MatchSpy	Class for classifying matching documents by their values
Xapian::PositionIterator	An iterator pointing to items in a list of positions
Xapian::PostingIterator	An iterator pointing to items in a list of postings
Xapian::ValueRangeProcessor	Base class for value range processors


C++ Classes we need to write:

Pike-based stopper bridge.
Pike-based stemmer bridge.

Exception handling needs to be improved.
