Added a mainpage to doxygen.

include/libssh/priv.h

@@ -30,6 +30,18 @@
 #ifndef _LIBSSH_PRIV_H
 #define _LIBSSH_PRIV_H
 
+/**
+ * @mainpage
+ * This manual documents the libssh C API.
+ *
+ * There are several other places to look for libssh information, such as the
+ * <a href="http://dev.libssh.org/wiki/Tutorial" target="_blank">tutorial</a>
+ * and the specification; those can be found at the <a
+ * href="http://www.libssh.org/" target="_blank">libssh website</a>.
+ *
+ * To be continued...
+ */
+
 #include "config.h"
 
 #ifdef _MSC_VER