[Kst] New header to install for external datasources

[Brisset, Nicolas]

Hi,

I've just come back and updated kst to the latest svn. I have had to
recompile everything, including external (read: built outside of the kst
source tree) datasources, and there I had the following problem:

/S/KDE/beta/include/rwlock.h:25:30: kstwaitcondition.h: No such file or
directory

I believe that header is not installed in $prefix/include and
datasources now seem to require it... 

Nicolas