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_venv.py b/Lib/test/test_venv.py
index 228aa8d..9724d9e 100644
--- a/Lib/test/test_venv.py
+++ b/Lib/test/test_venv.py
@@ -345,7 +345,7 @@
         """
         Test that the multiprocessing is able to spawn.
         """
-        # Issue bpo-36342: Instanciation of a Pool object imports the
+        # Issue bpo-36342: Instantiation of a Pool object imports the
         # multiprocessing.synchronize module. Skip the test if this module
         # cannot be imported.
         import_module('multiprocessing.synchronize')