Remove superfluous #includes

[[Imported from SVN: r8176]]

dune/solvers/test/genericvectortoolstest.cc

 #include <config.h>
 
-#include <stdio.h>
 #include <cmath>
 
 #include <dune/common/exceptions.hh>

dune/solvers/test/lowrankoperatortest.cc

 #include <config.h>
 
-#include <stdio.h>
 #include <cmath>
 
 #include <dune/common/exceptions.hh>

dune/solvers/test/nulloperatortest.cc

 #include <config.h>
 
-#include <stdio.h>
 #include <cmath>
 
 #include <dune/common/exceptions.hh>

dune/solvers/test/sumoperatortest.cc

 #include <config.h>
 
-#include <stdio.h>
 #include <cmath>
 
 #include <dune/common/exceptions.hh>