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/application.c b/src/application.c
index 8f37c93..e7c8e0f 100644
--- a/src/application.c
+++ b/src/application.c
@@ -22,7 +22,7 @@
  */
 
 /*! \file application.c
- *  \brief Routines for helping with the osmocom application setup.
+ *  Routines for helping with the osmocom application setup.
  */
 
 /*! \mainpage libosmocore Documentation
@@ -90,7 +90,7 @@
 	log_targets_reopen();
 }
 
-/*! \brief Ignore \ref SIGPIPE, \ref SIGALRM, \ref SIGHUP and \ref SIGIO */
+/*! Ignore \ref SIGPIPE, \ref SIGALRM, \ref SIGHUP and \ref SIGIO */
 void osmo_init_ignore_signals(void)
 {
 	/* Signals that by default would terminate */
@@ -106,7 +106,7 @@
 #endif
 }
 
-/*! \brief Initialize the osmocom logging framework
+/*! Initialize the osmocom logging framework
  *  \param[in] log_info Array of available logging sub-systems
  *  \returns 0 on success, -1 in case of error
  *
@@ -125,7 +125,7 @@
 	return 0;
 }
 
-/*! \brief Turn the current process into a background daemon
+/*! Turn the current process into a background daemon
  *
  * This function will fork the process, exit the parent and set umask,
  * create a new session, close stdin/stdout/stderr and chdir to /tmp