Manifest updates and fixes

Change 'download entry' to 'download entry tarball' as 'download entry' can be
slightly ambiguous: is it the source file or is it the entire entry? Perhaps
'download entire entry' could also be used but that might be going too far.

Change 'markdown source for index.html' to 'markdown source for this web page'
to match the index.html description in the manifest and because it makes more
sense this way.

Changed order of a.out.h and gentab.c in 1984/mullender in manifest: since
a.out.h description refers to gentab.c (as it's used in gentab.c) list gentab.c
first.

With this commit notwithstanding any possible manifest changes (which would
likely be for all other entries too) the index.html files of the entries from
1984 should be considered completely reviewed. The 1984/index.html file might
be done too but this depends on a discussion taking place.

2004/gavin/.entry.json

@@ -95,7 +95,7 @@
 	    "OK_to_edit" : false,
 	    "display_as" : "tbz2",
 	    "display_via_github" : false,
-	    "entry_text" : "download entry"
+	    "entry_text" : "download entry tarball"
 	},
 	{
 	    "file_path" : "index.html",
@@ -135,7 +135,7 @@
 	    "OK_to_edit" : true,
 	    "display_as" : "markdown",
 	    "display_via_github" : true,
-	    "entry_text" : "markdown source for index.html"
+	    "entry_text" : "markdown source for this web page"
 	},
 	{
 	    "file_path" : "gavin.md",

2004/gavin/index.html

@@ -290,12 +290,12 @@ at which a Linux bootloader loads an x86 kernel image).</p>
 <li><a href="img/fs.tar">img/fs.tar</a> - tar of root file system</li>
 <li><a href="img/kernel">img/kernel</a> - Linux kernel x86 boot executable zImage</li>
 <li><a href="prim">prim</a> - prime number printing program</li>
-<li><a href="2004_gavin.tar.bz2">2004_gavin.tar.bz2</a> - download entry</li>
+<li><a href="2004_gavin.tar.bz2">2004_gavin.tar.bz2</a> - download entry tarball</li>
 </ul>
 <h2 id="secondary-files">Secondary files</h2>
 <ul>
 <li><a href="index.html">index.html</a> - this web page</li>
-<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2004/gavin/README.md">README.md</a> - markdown source for index.html</li>
+<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2004/gavin/README.md">README.md</a> - markdown source for this web page</li>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2004/gavin/.entry.json">.entry.json</a> - description of entry in JSON</li>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2004/gavin/gavin.md">gavin.md</a> - markdown source for gavin.html</li>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2004/gavin/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>