fix HTML problems associated with leading ---'s

Please do not use "**---**" in markdown lines to separate sections.

This causes `pandoc(1)` to generate "**\<hr />**".

The "**\<hr />**" has no effect in standard HTML 5 and interacts
badly with unquoted attribute values.

If a horizontal line is really needed, use "**\<hr>**".

If a short line is needed, use: "**\<hr
style="width:10%;text-align:left;margin-left:0">**"

1998/df/README.md

@@ -118,7 +118,7 @@ reverse them. Anyone out there should have enough discipline and
 rot13 shouldn't be required, really. After all, we are not children
 anymore :-)
 
----
+<hr style="width:10%;text-align:left;margin-left:0">
 
 This paragraph is not part of the author's remarks, but is a helpful
 gift from the judges; if you read too fast to stop yourself, this should
@@ -126,7 +126,7 @@ give you enough time to stop, which you really need to do RIGHT NOW if
 you don't want to read the spoilers, which really do spoil everything,
 we mean it.
 
----
+<hr style="width:10%;text-align:left;margin-left:0">
 
 The source file needs to be present because the words are read from
 it. The wordlist is encoded within the source using a 24 entry

1998/df/index.html

@@ -237,13 +237,13 @@ rot13 spoilers since it is somewhat complicated on a Mac to
 reverse them. Anyone out there should have enough discipline and
 rot13 shouldn’t be required, really. After all, we are not children
 anymore :-)</p>
-<hr />
+<hr style="width:10%;text-align:left;margin-left:0">
 <p>This paragraph is not part of the author’s remarks, but is a helpful
 gift from the judges; if you read too fast to stop yourself, this should
 give you enough time to stop, which you really need to do RIGHT NOW if
 you don’t want to read the spoilers, which really do spoil everything,
 we mean it.</p>
-<hr />
+<hr style="width:10%;text-align:left;margin-left:0">
 <p>The source file needs to be present because the words are read from
 it. The wordlist is encoded within the source using a 24 entry
 sliding dictionary where lowercase letters are offsets into the

1998/dorssel/dorssel.html

@@ -264,7 +264,7 @@ mind ;-)</p>
     l[12] - l[14]   strspn argument
     l[34]           terminator for backward decoding
     l[35] - l[998]  input line</code></pre>
-<hr />
+<hr style="width:10%;text-align:left;margin-left:0">
 <p>Selected notes:
 - We don’t need to declare <code>isalnum(3)</code> (or include ctype.h) as its implicit
 declaration is correct (int argument, int result). This is not so for
@@ -276,7 +276,7 @@ whereas it is not. Well, it is, but there is a sequence point in between.
 - lclint 2.4b parses line 13 as <error>, whereas it is correct code.
 - lclint 2.4b is positive the second <code>while</code> loop is infinite, whereas it is
 not.</p>
-<hr />
+<hr style="width:10%;text-align:left;margin-left:0">
 <p>.. - …. .. -. -.- - …. .. … … .–. — .. .-.. . .-. .. … – — .-. . — -… ..-. ..- … -.-. .- - . -.. - …. .- -. - …. . .–. .-. — –. .-. .- –</p>
 <p>. -..- . .-. -.-. .. … .
 -.-. …. .- -. –. . - …. . .–. .-. — –. .-. .- – … — .. - -.. — . … -. — - … …. — ..- -</p>

1998/dorssel/dorssel.md

@@ -188,7 +188,7 @@ Summary of the use of l[999]:
     l[35] - l[998]  input line
 ```
 
----
+<hr style="width:10%;text-align:left;margin-left:0">
 
 Selected notes:
 - We don't need to declare `isalnum(3)` (or include ctype.h) as its implicit
@@ -202,7 +202,7 @@ Selected notes:
 - lclint 2.4b is positive the second `while` loop is infinite, whereas it is
   not.
 
----
+<hr style="width:10%;text-align:left;margin-left:0">
 
 ..  - .... .. -. -.-  - .... .. ...  ... .--. --- .. .-.. . .-.  .. ...  -- --- .-. .  --- -... ..-. ..- ... -.-. .- - . -..  - .... .- -.  - .... .  .--. .-. --- --. .-. .- --