[bugfix] Add missing include to eigenvaluetest.

At least Clang 3.2 complains.
(cherry picked from commit d4014751)

Signed-off-by: Markus Blatt <markus@dr-blatt.de>

dune/common/test/eigenvaluestest.cc

@@ -15,6 +15,7 @@
 #include <dune/common/fvector.hh>
 #include <dune/common/dynmatrixev.hh>
 
+#include <algorithm>
 #include <complex>