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

Based on patch by Ville Skyttä.
diff --git a/Lib/platform.py b/Lib/platform.py
index 63455ce..6e264f1 100755
--- a/Lib/platform.py
+++ b/Lib/platform.py
@@ -63,7 +63,7 @@
 #            though
 #    0.5.2 - fixed uname() to return '' instead of 'unknown' in all
 #            return values (the system uname command tends to return
-#            'unknown' instead of just leaving the field emtpy)
+#            'unknown' instead of just leaving the field empty)
 #    0.5.1 - included code for slackware dist; added exception handlers
 #            to cover up situations where platforms don't have os.popen
 #            (e.g. Mac) or fail on socket.gethostname(); fixed libc