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/Python/getopt.c b/Python/getopt.c
index 1a7db3f..89f7734 100644
--- a/Python/getopt.c
+++ b/Python/getopt.c
@@ -20,7 +20,7 @@
  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  *
  * Nevertheless, I would like to know about bugs in this library or
- * suggestions for improvment.  Send bug reports and feedback to
+ * suggestions for improvement.  Send bug reports and feedback to
  * davegottner@delphi.com.
  *---------------------------------------------------------------------------*/