fix all HTML headers

Renamed `ioccc.ico` to `favicon.ico`.

Correctly added use of `favicon.ico` to all constructed HTML headers.
Fixed the smart quote in HTML elements problem.

Moved HTML "DO NOT EDIT" comments down below at the bottom of the
HTML phase 1 section.  According to to the Nu Html Checker, a charset
attribute on a meta element found after the first 1024 bytes.

Changed `bin/md2html.sh` VERSION from "1.1.3 2024-03-28"
to "1.2 2024-03-30".

Improved `bin/gen-status.sh` to adjust the "status_update" value
only when the "contest_status" is changed.

Performed a `make www` to perform and test the above under macOS.

status.json

@@ -2,6 +2,6 @@
     "no_comment" : "mandatory comment: because comments were removed from the original JSON spec",
     "IOCCC_status_version" : "1.0 2024-03-09",
     "contest_status" : "closed",
-    "news_update" : "2024-03-30T21:31:22+00:00",
-    "status_update" : "2024-03-30T21:31:34+00:00"
+    "news_update" : "2024-03-20T06:52:56+00:00",
+    "status_update" : "2024-03-31T05:02:06+00:00"
 }