Update the doxygen configuration file.
Minor updates/fixes to the source documentation.
diff --git a/doxygen/header.html b/doxygen/header.html
index bab2841..3969315 100644
--- a/doxygen/header.html
+++ b/doxygen/header.html
@@ -2,7 +2,7 @@
<link href="doxygen.css" rel="stylesheet" type="text/css">
</head>
<body><center>
-<a href="../core/index.html">core</a>
+<a href="../main/index.html">core</a>
<a href="../array_cache/index.html">array_cache</a>
<a href="../math/index.html">math</a>
<a href="../swrast/index.html">swrast</a>