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/include/osmocom/core/application.h b/include/osmocom/core/application.h
index ecaeaa8..266fa9b 100644
--- a/include/osmocom/core/application.h
+++ b/include/osmocom/core/application.h
@@ -2,16 +2,16 @@
 
 /*!
  * \file application.h
- * \brief Routines for helping with the osmocom application setup.
+ * Routines for helping with the osmocom application setup.
  */
 
-/*! \brief information containing the available logging subsystems */
+/*! information containing the available logging subsystems */
 struct log_info;
 
-/*! \brief one instance of a logging target (file, stderr, ...) */
+/*! one instance of a logging target (file, stderr, ...) */
 struct log_target;
 
-/*! \brief the default logging target, logging to stderr */
+/*! the default logging target, logging to stderr */
 extern struct log_target *osmo_stderr_target;
 
 void osmo_init_ignore_signals(void);