Issue #27626: Spelling fixes in docs, comments and internal names

Based on patch by Ville Skyttä.
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 68285b8..f91501b 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -1747,7 +1747,7 @@
 PyDoc_STRVAR(chain_from_iterable_doc,
 "chain.from_iterable(iterable) --> chain object\n\
 \n\
-Alternate chain() contructor taking a single iterable argument\n\
+Alternate chain() constructor taking a single iterable argument\n\
 that evaluates lazily.");
 
 static PyMethodDef chain_methods[] = {