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/Include/pymath.h b/Include/pymath.h
index 6cf69f9..f869724 100644
--- a/Include/pymath.h
+++ b/Include/pymath.h
@@ -125,7 +125,7 @@
 
 /* Py_IS_FINITE(X)
  * Return 1 if float or double arg is neither infinite nor NAN, else 0.
- * Some compilers (e.g. VisualStudio) have intrisics for this, so a special
+ * Some compilers (e.g. VisualStudio) have intrinsics for this, so a special
  * macro for this particular test is useful
  * Note: PC/pyconfig.h defines Py_IS_FINITE as _finite
  */