Reword the recent deobfuscation changes

In most cases the word was changed to 'obfuscation' as it was about
obfuscation, not deobfuscation. In some cases like 1995/leo since the
file was (in 1995/leo) about a secret switch it was changed to
'secret.md' (and 'secret.html') but there were others like that as well.

One entry had the words 'spoiling the size rule' but this had been
changed to 'deobfuscating the size rule' which was obviously wrong.

In the latter YYYY/README.md files the judges had written after some
entries (brief summaries) '...

    ...We'll stop spouting spoilers now. Have fun exploring all the
    entries!

but that was changed to:

    ...We'll stop spouting deobfuscation information now. Have fun
    exploring all the entries!

which wasn't really about deobfuscation but just a brief summary of what
the entries did.

And in the most problematic case (at least for me :-), 2018/ferguson) I
had put a joke in:

    ... but it's the only Easter egg I won't spoil

but it was changed to 'won't deobfuscate' which not only is not what it
is but it spoilt the joke.

In some cases the word was changed back to 'SPOILER' (or similar) but in
most cases not. I believe it should be better now. There are some
caveats, however, as below.

Although make find_missing_links is okay I do not remember if this will
catch links that refer to '%%REPO_URL%%' or other pandoc tokens. This
means I might have to go back to some earlier years to verify links are
okay. That should not take that much time I hope.

It might also be that some wording can still be improved some but it is
hoped this will be discovered when checking links and looking over the
manifest (which obviously changed).

2011/fredriksson/README.md

@@ -199,7 +199,7 @@ Just say
   (Btw, tcc has its roots in IOCCC...)
 
 
-### Deobfuscation
+### Obfuscation
 
 * The initialized char array includes the source code of the real program,
   as well as its name and commands to build and run it, all

2011/fredriksson/index.html

@@ -536,7 +536,7 @@ C99, or long lines as an extension. This code has been tested on:</p></li>
 <li><p>AIX 5.3, IBM eServer p5-550, gcc 3.3.3 and AIX CC Version 6</p>
 <p>(Btw, tcc has its roots in IOCCC…)</p></li>
 </ul>
-<h3 id="deobfuscation">Deobfuscation</h3>
+<h3 id="obfuscation">Obfuscation</h3>
 <ul>
 <li>The initialized char array includes the source code of the real program,
 as well as its name and commands to build and run it, all

2011/hou/README.md

@@ -110,7 +110,7 @@ the actual `argv` strings to be writable, though.
 - Some seemingly redundant code works to eliminate warnings and evade a gcc bug.
 
 
-### Deobfuscation
+### Spoilers
 
 The parser parses function names, subtraction, and division as single-letter
 unary operators. A bitmask encoded hash table is used to check no-ops/digits

2011/hou/index.html

@@ -462,7 +462,7 @@ the actual <code>argv</code> strings to be writable, though.</li>
 <li>This program doesn’t work with <code>%e</code> style numbers like <code>1e-4</code>.</li>
 <li>Some seemingly redundant code works to eliminate warnings and evade a gcc bug.</li>
 </ul>
-<h3 id="deobfuscation">Deobfuscation</h3>
+<h3 id="spoilers">Spoilers</h3>
 <p>The parser parses function names, subtraction, and division as single-letter
 unary operators. A bitmask encoded hash table is used to check no-ops/digits
 and another hash function maps the ASCII to a function ordinal, which is then

2011/zucker/README.md

@@ -153,7 +153,7 @@ reflection ray at an object's surface, given the incoming
 direction and surface normal.
 
 
-#### Further deobfuscation:
+#### Further details:
 
 The program is not quite a traditional [ray
 tracer](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)), but a "[sphere

2011/zucker/index.html

@@ -480,7 +480,7 @@ by the source code itself: the geometric construction of a
 reflection ray at an object’s surface, given the incoming
 direction and surface normal.</p></li>
 </ul>
-<h4 id="further-deobfuscation">Further deobfuscation:</h4>
+<h4 id="further-details">Further details:</h4>
 <p>The program is not quite a traditional <a href="https://en.wikipedia.org/wiki/Ray_tracing_(graphics)">ray
 tracer</a>, but a “<a href="sphere-tracing.pdf">sphere
 tracer</a>” which uses distance fields to encode proximity to