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/gsm/a5.c b/src/gsm/a5.c
index 23cbe0c..f21554f 100644
--- a/src/gsm/a5.c
+++ b/src/gsm/a5.c
@@ -28,7 +28,7 @@
 
 /*! \addtogroup crypto
  *  @{
- *  \brief Osmocom GSM/GPRS ciphering algorithm implementation
+ *  Osmocom GSM/GPRS ciphering algorithm implementation
  */
 
 /*! \file gsm/a5.c */
@@ -50,7 +50,7 @@
 /* A5/3&4                                                                   */
 /* ------------------------------------------------------------------------ */
 
-/*! \brief Generate a GSM A5/4 cipher stream
+/*! Generate a GSM A5/4 cipher stream
  *  \param[in] key 16 byte array for the key (as received from the SIM)
  *  \param[in] fn Frame number
  *  \param[out] dl Pointer to array of ubits to return Downlink cipher stream
@@ -79,7 +79,7 @@
        }
 }
 
-/*! \brief Generate a GSM A5/3 cipher stream
+/*! Generate a GSM A5/3 cipher stream
  *  \param[in] key 8 byte array for the key (as received from the SIM)
  *  \param[in] fn Frame number
  *  \param[out] dl Pointer to array of ubits to return Downlink cipher stream
@@ -119,7 +119,7 @@
 #define A5_R3_TAPS	0x700080 /* x^23 + x^22 + x^21 + x^8 + 1 */
 #define A5_R4_TAPS	0x010800 /* x^17 + x^12 + 1 */
 
-/*! \brief Computes parity of a 32-bit word
+/*! Computes parity of a 32-bit word
  *  \param[in] x 32 bit word
  *  \return Parity bit (xor of all bits) as 0 or 1
  */
@@ -133,7 +133,7 @@
 	return (0x6996 >> x) & 1;
 }
 
-/*! \brief Compute majority bit from 3 taps
+/*! Compute majority bit from 3 taps
  *  \param[in] v1 LFSR state ANDed with tap-bit
  *  \param[in] v2 LFSR state ANDed with tap-bit
  *  \param[in] v3 LFSR state ANDed with tap-bit
@@ -145,7 +145,7 @@
 	return (!!v1 + !!v2 + !!v3) >= 2;
 }
 
-/*! \brief Compute the next LFSR state
+/*! Compute the next LFSR state
  *  \param[in] r Current state
  *  \param[in] mask LFSR mask
  *  \param[in] taps LFSR taps
@@ -166,7 +166,7 @@
 #define A51_R2_CLKBIT	0x000400
 #define A51_R3_CLKBIT	0x000400
 
-/*! \brief GSM A5/1 Clocking function
+/*! GSM A5/1 Clocking function
  *  \param[in] r Register state
  *  \param[in] force Non-zero value disable conditional clocking
  */
@@ -191,7 +191,7 @@
 		r[2] = _a5_12_clock(r[2], A5_R3_MASK, A5_R3_TAPS);
 }
 
-/*! \brief GSM A5/1 Output function
+/*! GSM A5/1 Output function
  *  \param[in] r Register state
  *  \return The A5/1 output function bit
  */
@@ -203,7 +203,7 @@
 		(r[2] >> (A5_R3_LEN-1));
 }
 
-/*! \brief Generate a GSM A5/1 cipher stream
+/*! Generate a GSM A5/1 cipher stream
  *  \param[in] key 8 byte array for the key (as received from the SIM)
  *  \param[in] fn Frame number
  *  \param[out] dl Pointer to array of ubits to return Downlink cipher stream
@@ -278,7 +278,7 @@
 #define A52_R4_CLKBIT1	0x000008
 #define A52_R4_CLKBIT2	0x000080
 
-/*! \brief GSM A5/2 Clocking function
+/*! GSM A5/2 Clocking function
  *  \param[in] r Register state
  *  \param[in] force Non-zero value disable conditional clocking
  */
@@ -305,7 +305,7 @@
 	r[3] = _a5_12_clock(r[3], A5_R4_MASK, A5_R4_TAPS);
 }
 
-/*! \brief GSM A5/2 Output function
+/*! GSM A5/2 Output function
  *  \param[in] r Register state
  *  \return The A5/2 output function bit
  */
@@ -324,7 +324,7 @@
 	return b;
 }
 
-/*! \brief Generate a GSM A5/1 cipher stream
+/*! Generate a GSM A5/1 cipher stream
  *  \param[in] key 8 byte array for the key (as received from the SIM)
  *  \param[in] fn Frame number
  *  \param[out] dl Pointer to array of ubits to return Downlink cipher stream
@@ -398,7 +398,7 @@
 	osmo_a5(2, key, fn, dl, ul);
 }
 
-/*! \brief Main method to generate a A5/x cipher stream
+/*! Main method to generate a A5/x cipher stream
  *  \param[in] n Which A5/x method to use
  *  \param[in] key 8 or 16 (for a5/4) byte array for the key (as received from the SIM)
  *  \param[in] fn Frame number