Fix various typos reported to python-docs.

Doc/ref/refa1.tex

@@ -160,10 +160,10 @@ No feature description will ever be deleted from \module{__future__}.
 \section{Nested scopes \label{nested-scopes}}
 \indexii{nested}{scopes}
 
-This section defines the new scoping semantics that will be introduced
-in Python 2.2.  They are available in Python 2.1 by using the future
+This section defines the new scoping semantics that were introduced
+in Python 2.2.  They were available in Python 2.1 by using the future
 statement \samp{nested_scopes}.  This section begins with a bit of
-terminology. 
+terminology.
 
 \subsection{Definitions and rules \label{definitions}}
 
@@ -177,7 +177,7 @@ a unit.  The following are blocks: a module, a function body, and a
 class definition.
 
 A \dfn{scope} defines the visibility of a name within a block.  If a
-local variable is defined in a block, it's scope includes that block.
+local variable is defined in a block, its scope includes that block.
 If the definition occurs in a function block, the scope extends to any
 blocks contained within the defining one, unless a contained block
 introduces a different binding for the name.  The scope of names