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/strrb.c b/src/strrb.c
index 69c4dda..0c56be2 100644
--- a/src/strrb.c
+++ b/src/strrb.c
@@ -26,7 +26,7 @@
  */
 
 /*! \file strrb.c
- *  \brief Lossy string ringbuffer for logging; keeps newest messages.
+ *  Lossy string ringbuffer for logging; keeps newest messages.
  */
 
 #include <stdio.h>
@@ -49,7 +49,7 @@
  * is the case unless this is the first time the ringbuffer becomes full).
 */
 
-/*! \brief Create an empty, initialized osmo_strrb.
+/*! Create an empty, initialized osmo_strrb.
  *  \param[in] ctx The talloc memory context which should own this.
  *  \param[in] rb_size The number of message slots the osmo_strrb can hold.
  *  \returns A struct osmo_strrb* on success, NULL in case of error.
@@ -87,7 +87,7 @@
 	return NULL;
 }
 
-/*! \brief Check if an osmo_strrb is empty.
+/*! Check if an osmo_strrb is empty.
  *  \param[in] rb The osmo_strrb to check.
  *  \returns True if the osmo_strrb is empty, false otherwise.
  */
@@ -96,7 +96,7 @@
 	return rb->end == rb->start;
 }
 
-/*! \brief Return a pointer to the Nth string in the osmo_strrb.
+/*! Return a pointer to the Nth string in the osmo_strrb.
  * \param[in] rb The osmo_strrb to search.
  * \param[in] string_index The index sought (N), zero-indexed.
  *
@@ -130,7 +130,7 @@
 	return (bufi < rb->end) || (bufi >= rb->start);
 }
 
-/*! \brief Count the number of log messages in an osmo_strrb.
+/*! Count the number of log messages in an osmo_strrb.
  *  \param[in] rb The osmo_strrb to count the elements of.
  *
  *  \returns The number of log messages in the osmo_strrb.
@@ -143,7 +143,7 @@
 	return rb->end - rb->start;
 }
 
-/*! \brief Add a string to the osmo_strrb.
+/*! Add a string to the osmo_strrb.
  * \param[in] rb The osmo_strrb to add to.
  * \param[in] data The string to add.
  *