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

Based on patch by Ville Skyttä.
diff --git a/Lib/datetime.py b/Lib/datetime.py
index 2f94218..a2178c7 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -706,7 +706,7 @@
 
     @classmethod
     def fromordinal(cls, n):
-        """Contruct a date from a proleptic Gregorian ordinal.
+        """Construct a date from a proleptic Gregorian ordinal.
 
         January 1 of year 1 is day 1.  Only the year, month and day are
         non-zero in the result.