improve data on author_handle.json files

Updated URLs, Email addresses, GitHub handles,
Mastodon handles, and locations of various IOCCC winning authors.

author/David_Korn.json

@@ -8,7 +8,7 @@
     "location_name" : "United States of America",
     "email" : "dgk@research.att.com",
     "url" : "http://www.kornshell.com/~dgk/",
-    "alt_url" : null,
+    "alt_url" : "https://www.linkedin.com/in/david-korn-b23185/",
     "deprecated_twitter_handle" : null,
     "mastodon" : null,
     "mastodon_url" : null,