Issue #27076: Doc, comment and tests spelling fixes

Most fixes to Doc/ and Lib/ directories by Ville Skyttä.
diff --git a/Lib/pickle.py b/Lib/pickle.py
index 7512787..7760425 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -995,7 +995,7 @@
         meets this interface.
 
         Optional keyword arguments are *fix_imports*, *encoding* and
-        *errors*, which are used to control compatiblity support for
+        *errors*, which are used to control compatibility support for
         pickle stream generated by Python 2.  If *fix_imports* is True,
         pickle will try to map the old Python 2 names to the new names
         used in Python 3.  The *encoding* and *errors* tell pickle how