Here is the initial version of the Emacs package that provides support
for Texinfo XML format in the Emacs Info browser.  This format is
generated by the command `makeinfo --xml' that maps Texinfo markup
commands into XML syntax.

The current implementation uses a lot of defadvices on basic info.el
functions.  This was done for adding new format seamlessly, and leaving
old Info API for the new format.  Later these functions could be modified
to allow switching between different Info formats natively.

I'd like to hear all comments about whether this is the right direction
and so on.  Thanks.