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/loggingrb.c b/src/loggingrb.c
index 3fb38ca..64033fc 100644
--- a/src/loggingrb.c
+++ b/src/loggingrb.c
@@ -24,7 +24,7 @@
  */
 
 /*! \file loggingrb.c
- *  \brief libosmocore logging backend for a ring-buffer of last log messages
+ *  libosmocore logging backend for a ring-buffer of last log messages
  */
 
 #include <osmocom/core/strrb.h>
@@ -37,7 +37,7 @@
 	osmo_strrb_add(target->tgt_rb.rb, log);
 }
 
-/*! \brief Return the number of log strings in the osmo_strrb-backed target.
+/*! Return the number of log strings in the osmo_strrb-backed target.
  *  \param[in] target The target to search.
  *
  *  \return The number of log strings in the osmo_strrb-backed target.
@@ -47,7 +47,7 @@
 	return osmo_strrb_elements(target->tgt_rb.rb);
 }
 
-/*! \brief Return the capacity of the osmo_strrb-backed target.
+/*! Return the capacity of the osmo_strrb-backed target.
  *  \param[in] target The target to search.
  *
  * Note that this is the capacity (aka max number of messages).
@@ -60,7 +60,7 @@
 	return rb->size - 1;
 }
 
-/*! \brief Return the nth log entry in a target.
+/*! Return the nth log entry in a target.
  *  \param[in] target The target to search.
  *  \param[in] logindex The index of the log entry/error message.
  *
@@ -71,7 +71,7 @@
 	return osmo_strrb_get_nth(target->tgt_rb.rb, logindex);
 }
 
-/*! \brief Create a new logging target for ringbuffer-backed logging.
+/*! Create a new logging target for ringbuffer-backed logging.
  *  \param[in] size The capacity (number of messages) of the logging target.
  *  \returns A log target in case of success, NULL in case of error.
  */