Typo fix: casted -> cast (in doc .txt files)

doc/extending/op.txt

@@ -333,7 +333,7 @@ In the following code, we use our new Op:
 
 Note that there is an implicit call to
 ``double.filter()`` on each argument, so if we give integers as inputs
-they are magically casted to the right type. Now, what if we try this?
+they are magically cast to the right type. Now, what if we try this?
 
 >>> x = double('x')
 >>> z = mul(x, 2)

doc/extending/type.txt

@@ -27,7 +27,7 @@ default values.
     .. method:: filter(value, strict=False, allow_downcast=None)
 
       This casts a value to match the Type and returns the
-      casted value. If ``value`` is incompatible with the Type,
+      cast value. If ``value`` is incompatible with the Type,
       the method must raise an exception. If ``strict`` is True, ``filter`` must return a
       reference to ``value`` (i.e. casting prohibited).
       If ``strict`` is False, then casting may happen, but downcasting should

doc/proposals/pfunc.txt

@@ -64,7 +64,7 @@ The proposal is for two new ways of creating a *shared* variable:
     
             :param value: A value to associate with this variable (a new container will be created).
     
-            :param strict: True -> assignments to .value will not be casted or copied, so they must
+            :param strict: True -> assignments to .value will not be cast or copied, so they must
             have the correct type.
     
             :param container: The container to use for this variable. Illegal to pass this as well
@@ -185,7 +185,7 @@ Corner cases and exotic examples can be found in the tests.
     
             :param mutable: True -> function is allowed to modify this argument.
     
-            :param strict: False -> function arguments may be copied or casted to match the
+            :param strict: False -> function arguments may be copied or cast to match the
             type required by the parameter `variable`.  True -> function arguments must exactly match the type
             required by `variable`.