Various fixes and updates

Make lines beginning (in markdown files) 'BTW' bold. Rebuilt the
respective html pages.

Slight update to abstract in two entries (1985/shapiro and
1994/shapiro). One is changing 'defines' to '#defines' and the other was
a typo fix.

Fixed make gen_next: added missing new files.

Various fixes in next/register.html (typos and other things).

2020/ferguson2/recode.html

@@ -914,7 +914,7 @@ think that I would give too much away? :)</p>
     4MU1MS3CA0KECHOLATBJSNPXVUFGZY
     4VW0SL1YB0IYJSLBECKTNAXGPUVHRF
     0MC4OH2CO1LATEUMBJCDFGHINOPRQS</code></pre>
-<p>BTW: what’s the middle of a list with even numbered items anyway?</p>
+<p><strong>BTW</strong>: what’s the middle of a list with even numbered items anyway?</p>
 <p>To help you out, though, this is how you might do the decrypting. Assuming that
 the key you wish to select is</p>
 <pre><code>    0EZ4PC1CC0PGTAQSOXWNMDRYKFUZEI</code></pre>