Compiler compatibility fixes; Reference assignment changed (if the lhs is initialized, the assignment goes to the referenced object, thus the reference is not rebound)

[SVN r20546]

libs/optional

@@ -1 +1 @@
-Subproject commit faa3c1962a7df0aa5fb261ccdf362d6cffd95a0a
+Subproject commit 3468bfb07ffeb761ef923c340a5c98a6369efc83