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/logging_syslog.c b/src/logging_syslog.c
index 6fe3c71..a80a31e 100644
--- a/src/logging_syslog.c
+++ b/src/logging_syslog.c
@@ -24,7 +24,7 @@
  */
 
 /*! \file logging_syslog.c
- *  \brief libosmocore logging output via syslog
+ *  libosmocore logging output via syslog
  */
 
 #include "../config.h"
@@ -65,7 +65,7 @@
 	syslog(logp2syslog_level(level), "%s", log);
 }
 
-/*! \brief Create a new logging target for syslog logging
+/*! Create a new logging target for syslog logging
  *  \param[in] ident syslog string identifier
  *  \param[in] option syslog options
  *  \param[in] facility syslog facility