Weak: Don't require wrapping/unwrapping of finalizers

To quote Simon Marlow,

    We don't expect users to ever write code that uses mkWeak# or
    finalizeWeak#, we have safe interfaces to these. Let's document the type
    unsafety and fix the problem with () without introducing any overhead.

Updates stm submodule.

1 files changed, 0 insertions, 0 deletions

diff --git a/libraries/stm b/libraries/stm
-Subproject 8fb3b3336971d784c091dbca674ae1401e506e7
+Subproject f7db2c3df86ec644e5e06baa8090a1cb525754e