Minor fixes

We exclude pdftex.map from file lookup (unless found)
So no warning message is given when we can't find 
pdftex.map

Some very minor fixes / enhancements not worth
writing down here.
New XML parser "luxor"

With the new xml parser we can get rid of
libxml2 bindings as well as the lpeg based
xml parser. No need for a special binary anymore.

The new xml parser seems to be as fast as
the xml bindings.

The reason behind this change is that compilation
of luatex with libxml2 bindings is not trivial. I've
wasted a lot of time on this.
Use three slashes in file uri on windows

This should be file:///c:/foo/bar.baz, not 
file://c:/foo/bar.baz. See
http://en.wikipedia.org/wiki/File_URI_scheme#Windows_2
for an explanation.
XML parser update (faster)
News table attribute "eval"

Allows execution of xpath expressions. The output
is discarded.

Can be used for sd:reset-alternating() to color
the rows in every table and always start at the
sd:reset-alternating(), changed sd:alternating()

I guess nobody uses sd:alternating() so I introduced
a change that makes it more future compatible.

Add sd:reset-alternating() to reset a sequence. Very
useful in alternating table row backgrounds.
Allow TableHead in SetVariable, small err msg

Added a small error message (and visual marker) if
the publisher can't parse the width attribute in the
command 'textblock'.
Re-enable sdluatex binary

I think it's better to look for a sdluatex binary
first. On systems where we have both I don't want
to rely on the luatex version to match the publisher
internals.
New command sp clean, change name of dataset

New: sp clean removes temporary files. 
Changed name of xml files to 
  (jobname)-(name).dataxml
so that we can easily delete the file with sp clean.
Remove bit.lua

This was necessary with our lpeg xml parser