Issue #27076: Doc, comment and test function name spelling fixes

Most fixes to Doc/ and Lib/ directories by Ville Skyttä.
diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 6baaccf..62b36bd 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -1740,7 +1740,7 @@
 
         # http://en.wikipedia.org/wiki/Cuboctahedron
         # 8 triangular faces and 6 square faces
-        # 12 indentical vertices each connecting a triangle and square
+        # 12 identical vertices each connecting a triangle and square
 
         g = cube(3)
         cuboctahedron = linegraph(g)            # V( --> {V1, V2, V3, V4}