[Qexo-general] some Qexo improvements

[Per Bothner]

I checked in some improvements:

The '|' or 'union' operator is now implemented.

The 'declare xmlspace' declaration is implemented, which should now 
correctly handle "Boundary whitespace" in element constructors.

Optional function returns are now handled.  Some type specifiers would 
generate bad bytecode; these should now be fixed.

The path expression re-write seems to be working pretty well.  However, 
 there are still a few pieces missing; there may be a performance 
regression because old optimizations need to be retro-fitted; and the 
code needs to be cleaned up here and there.  I'm also going through a 
lot of the "Use Cases" that the W3C working groaup put out, and getting 
them to work.

Bottom line: We're close to having a complete implementation of xpath 
functionality.  I.e. most of XPath 2.0, ignoring that many standard 
functions are still missing, we ignore comment and processing 
instructions nodes, we don't have 'some' or 'every' expressions, etc.
--
        --Per Bothner
address@hidden   http://per.bothner.com/