Mutable Expression concept requires:

 assignment (default fails as reference type) and swap
 Use deep semantics as in a C++ reference


[SVN r25305]

libs/numeric/ublas

@@ -1 +1 @@
-Subproject commit 12f9c0cf75c9b128fa703acfcd84c6afa73af872
+Subproject commit 3fbe29f6bc24b19957a4c17bf644d95afe5b302b