update/extend doxygen documentation

It's a pity that even with this patch we still are fare away from having
the whole API documented.  However, at least we have a more solid
foundation.  Updates not only extend the documentation, but also make
sure it is rendered properly in the doxygen HTML.

Change-Id: I1344bd1a6869fb00de7c1899a8db93bba9bafce3
diff --git a/src/vty/vty.c b/src/vty/vty.c
index 01d5ec0..2ec9538 100644
--- a/src/vty/vty.c
+++ b/src/vty/vty.c
@@ -14,7 +14,7 @@
  * routines in libosmovty are not thread-safe.  If you must use them in
  * a multi-threaded context, you have to add your own locking.
  *
- * libosmocovty is developed as part of the Osmocom (Open Source Mobile
+ * libosmovty is developed as part of the Osmocom (Open Source Mobile
  * Communications) project, a community-based, collaborative development
  * project to create Free and Open Source implementations of mobile
  * communications systems.  For more information about Osmocom, please