datarootdir confusion

[Sven Panne]

Just a note, because it is too late for me to fix and test this: The logic in 
mk/config.mk.in regarding datarootdir is wrong and leads to incorrect 
directories.  Autoconf 2.60 introduced datarootdir, and defines the following 
defaults:

   datadir = ${datarootdir}
   infodir = ${datarootdir}/info
   mandir  = ${datarootdir}/man

Therefore, we *must* have a line

   datarootdir := @datarootdir@

in config.mk.in before any possible use of it, otherwise @datadir@, @infodir@ 
and @mandir@ are ill-defined for autoconf >= 2.60. The current logic seems to 
be the other way round, which is wrong. Note that for older autoconfs the 
added line does no harm, as ${datarootdir} is simply not used for the 
defaults then and can have the strange value "@datarootdir@". See:

http://www.gnu.org/software/autoconf/manual/html_node/Changed-Directory-Variables.html

It would be nice if somebody could fix and test this, I'll probably have no 
spare time in the next few days.

Cheers,
   S.