Add RangeProcessor class to replace ValueRangeProcessor
ValueRangeProcessor is now deprecated.
RangeProcessor() has an operator()() method returning Xapian::Query,
whereas ValueRangeProcessor can only return a value range.
Combining of ranges over the same quantity with OP_OR is now handled by
an explicit "grouping" parameter, with a sensible default which works
for value range queries. Boolean term prefixes and FieldProcessor now
support "grouping" too, so ranges and other filters can now be
grouped together.
Fixes #663.
18 files changed: