fix compiler error in lu_decomposition for K != double

Backported from Martin's development branch,
minus some whitespace changes.  Thanks.

[[Imported from SVN: r6712]]

dune/common/densematrix.hh

@@ -729,12 +729,9 @@ namespace Dune
   {
     typedef typename FieldTraits<value_type>::real_type
     real_type;
-    typename FieldTraits<value_type>::real_type norm =
-      A.infinity_norm_real(); // for relative thresholds
-    typename FieldTraits<value_type>::real_type pivthres =
-      std::max(FMatrixPrecision<real_type>::absolute_limit(),norm*FMatrixPrecision<>::pivoting_limit());
-    typename FieldTraits<value_type>::real_type singthres =
-      std::max(FMatrixPrecision<real_type>::absolute_limit(),norm*FMatrixPrecision<>::singular_limit());
+    real_type norm = A.infinity_norm_real(); // for relative thresholds
+    real_type pivthres = std::max( FMatrixPrecision< real_type >::absolute_limit(), norm * FMatrixPrecision< real_type >::pivoting_limit() );
+    real_type singthres = std::max( FMatrixPrecision< real_type >::absolute_limit(), norm * FMatrixPrecision< real_type >::singular_limit() );
 
     // LU decomposition of A in A
     for (size_type i=0; i<rows(); i++)  // loop over all rows