Merge iostreams to release. Fixes #8315, #8385, #8460.

Not merging the fallthrough macro, as config support hasn't been merged yet.
And not merging the build changes, as I don't know if they're ready.


[SVN r84303]

libs/iostreams

@@ -1 +1 @@
-Subproject commit c20af5e60c6a6928e79b1f9e5413ed7fceb24035
+Subproject commit 22ad7ceb37865b9a38635306d5409a03a0510feb