Fix typos in comments, docs and test names (#15018)

* Fix typos in comments, docs and test names

* Update test_pyparse.py

account for change in string length

* Apply suggestion: splitable -> splittable

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: splitable -> splittable

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: Dealloccte -> Deallocate

Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Update posixmodule checksum.

* Reverse idlelib changes.
diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 5ea18f5..f7c399e 100644
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -2485,7 +2485,7 @@
 
 def test_testfile(): r"""
 Tests for the `testfile()` function.  This function runs all the
-doctest examples in a given file.  In its simple invokation, it is
+doctest examples in a given file.  In its simple invocation, it is
 called with the name of a file, which is taken to be relative to the
 calling module.  The return value is (#failures, #tests).