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/vector.c b/src/vty/vector.c
index c5a99af..b95e15c 100644
--- a/src/vty/vector.c
+++ b/src/vty/vector.c
@@ -27,6 +27,11 @@
 #include <osmocom/core/talloc.h>
 #include <string.h>
 
+/*! \addtogroup vector
+ *  @{
+ *  \brief Generic vector routines, used by VTY internally
+ */
+
 void *tall_vty_vec_ctx;
 
 /* Initialize vector : allocate memory and return vector. */
@@ -190,3 +195,5 @@
 
 	return count;
 }
+
+/*! @} */