doxygen: enable AUTOBRIEF, drop \brief

Especially for short descriptions, it is annoying to have to type \brief for
every single API doc.

Drop all \brief and enable the AUTOBRIEF feature of doxygen, which always takes
the first sentence of an API doc as the brief description.

Change-Id: I11a8a821b065a128108641a2a63fb5a2b1916e87
diff --git a/src/vty/stats_vty.c b/src/vty/stats_vty.c
index af69289..0557820 100644
--- a/src/vty/stats_vty.c
+++ b/src/vty/stats_vty.c
@@ -43,7 +43,7 @@
 
 /*! \addtogroup stats
  *  @{
- *  \brief VTY interface for statsd / statistic items
+ *  VTY interface for statsd / statistic items
  */
 
 /* containing version info */
@@ -576,7 +576,7 @@
 	return 1;
 }
 
-/*! \brief Add stats related commands to the VTY
+/*! Add stats related commands to the VTY
  *  Call this once during your application initialization if you would
  *  like to have stats VTY commands enabled.
  */