[sil] Add clarity to how load_weak [take] and store_weak effect an objects weak ref count.

Author: gottesmm

docs/SIL.rst

@@ -2827,6 +2827,12 @@ which must be an initialized weak reference.  The result is value of type
 ``$Optional<T>``, except that it is ``null`` if the heap object has begun
 deallocation.
 
+If ``[take]`` is specified then the underlying weak reference is invalidated
+implying that the weak reference count of the loaded value is decremented. If
+``[take]`` is not specified then the underlying weak reference count is not
+effected by this operation (i.e. it is a +0 weak ref count operation). In either
+case, the strong reference count will be incremented.
+
 This operation must be atomic with respect to the final ``strong_release`` on
 the operand heap object.  It need not be atomic with respect to ``store_weak``
 operations on the same address.
@@ -2845,7 +2851,9 @@ Initializes or reassigns a weak reference.  The operand may be ``nil``.
 
 If ``[initialization]`` is given, the weak reference must currently either be
 uninitialized or destroyed.  If it is not given, the weak reference must
-currently be initialized.
+currently be initialized and after the evaluation the value that was originally
+referenced by the weak reference will have its weak reference count decremented
+by 1.
 
 This operation must be atomic with respect to the final ``strong_release`` on
 the operand (source) heap object.  It need not be atomic with respect to