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

Most fixes to Doc/ and Lib/ directories by Ville Skyttä.
diff --git a/Lib/email/parser.py b/Lib/email/parser.py
index 2fcaf25..6dad32a 100644
--- a/Lib/email/parser.py
+++ b/Lib/email/parser.py
@@ -23,7 +23,7 @@
         textual representation of the message.
 
         The string must be formatted as a block of RFC 2822 headers and header
-        continuation lines, optionally preceeded by a `Unix-from' header.  The
+        continuation lines, optionally preceded by a `Unix-from' header.  The
         header block is terminated either by the end of the string or by a
         blank line.