Fixed bug introduced by Christian.

The check i>=0 is always true if i is unsigned!

[[Imported from SVN: r4830]]

common/fmatrix.hh

@@ -704,7 +704,7 @@ namespace Dune {
       }
 
       // U A^{-1} = Y
-      for (size_type i=n-1; i>=0; i--) {
+      for (size_type i=n-1; i!=0; i--) {
         for (size_type k=0; k<n; k++) {
           for (size_type j=i+1; j<n; j++)
             p[i][k] -= U[i][j]*p[j][k];
@@ -712,7 +712,7 @@ namespace Dune {
         }
       }
 
-      for(size_type i=n-1; i>=0; --i) {
+      for(size_type i=n-1; i!=0; --i) {
         if(i!=pivot[i])
           for(size_type j=0; j<n; ++j)
             std::swap(p[j][pivot[i]], p[j][i]);