Fix grammar, typos and markup in documentation and code comments

* Indent versionchanged at method level, not class level
* Mark up ``--help`` to avoid generating an en dash
* Use forward slash in Unix command line with a dollar sign ($) prompt
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 10fbcfe..ac81680 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -2169,7 +2169,7 @@
 PyDoc_STRVAR(_count_elements_doc,
 "_count_elements(mapping, iterable) -> None\n\
 \n\
-Count elements in the iterable, updating the mappping");
+Count elements in the iterable, updating the mapping");
 
 static PyObject *
 _count_elements(PyObject *self, PyObject *args)
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 46c99b5..89b0798 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -1012,7 +1012,7 @@
                                                            errors);
         if (self->encoder == NULL)
             goto error;
-        /* Get the normalized named of the codec */
+        /* Get the normalized name of the codec */
         res = _PyObject_GetAttrId(codec_info, &PyId_name);
         if (res == NULL) {
             if (PyErr_ExceptionMatches(PyExc_AttributeError))