[xml] libxml2 and libxslt wishlist

[mgrushinskiy comcast net]

I don't know if there is a separately maintained wishlist for these libraries.
But here are few features which would be nice to have there ;)

1. regexp exslt functions for libxslt
2. XUpdate processor (xmldb.org)
3. finished schemas
4. options to store original XML formatting in parsed tree representation
    (ex. if attributes are on separate lines, xmllint would output them 
    same way, at least with some option)

Thanks for doing good work on libxml/libxslt.
--Mikhail