Issue #27076: Doc, comment and test function name spelling fixes

Most fixes to Doc/ and Lib/ directories by Ville Skyttä.
diff --git a/Modules/datetimemodule.c b/Modules/datetimemodule.c
index f733fa1..e7fd349 100644
--- a/Modules/datetimemodule.c
+++ b/Modules/datetimemodule.c
@@ -197,7 +197,7 @@
         return _days_in_month[month];
 }
 
-/* year, month -> number of days in year preceeding first day of month */
+/* year, month -> number of days in year preceding first day of month */
 static int
 days_before_month(int year, int month)
 {
diff --git a/Modules/sha256module.c b/Modules/sha256module.c
index 2ce8d92..8f18faa 100644
--- a/Modules/sha256module.c
+++ b/Modules/sha256module.c
@@ -101,7 +101,7 @@
  * algorithms in a highly modular and flexible manner.
  *
  * The library is free for all purposes without any express
- * gurantee it works.
+ * guarantee it works.
  *
  * Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
  */
diff --git a/Modules/sha512module.c b/Modules/sha512module.c
index d7b3699..abc9021 100644
--- a/Modules/sha512module.c
+++ b/Modules/sha512module.c
@@ -111,7 +111,7 @@
  * algorithms in a highly modular and flexible manner.
  *
  * The library is free for all purposes without any express
- * gurantee it works.
+ * guarantee it works.
  *
  * Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
  */