Fix doxygen for autogenerated code

codegen/gen_actions.ysl2

@@ -55,7 +55,7 @@ tstylesheet {
              *
              *  @retval      true        if t2 is NULL and t1 is not, or the size of t1 is greater than t2, or
              *                           the first non-matching byte of t1 is greater than that of t2
-             *               false       otherwise
+             *  @retval      false       otherwise
              */
             static bool _TID_greater(TID_t *t1, TID_t *t2)
             {
@@ -85,7 +85,7 @@ tstylesheet {
              *  @param[in]   ident2          pointer to the second identity
              *
              *  @retval      true        if user_id and address match on both identities
-             *               false       otherwise
+             *  @retval      false       otherwise
              */
             static bool _same_identity(pEp_identity *ident1, pEp_identity *ident2)
             {
@@ -109,8 +109,8 @@ tstylesheet {
              *  @param[out]  found       true if an identity with matching unique identifiers is in the list, else false
              *
              *  @retval      PEP_ILLEGAL_VALUE        any of the input pointers are NULL
-             *               PEP_OUT_OF_MEMORY        if memory problems occur
-             *               PEP_STATUS_OK            otherwise
+             *  @retval      PEP_OUT_OF_MEMORY        if memory problems occur
+             *  @retval      PEP_STATUS_OK            otherwise
              */
             static PEP_STATUS _have_identity_in(identity_list *il, pEp_identity *ident, bool *found)
             {

codegen/gen_message_func.ysl2

@@ -108,10 +108,10 @@ void free_«@name»_state(PEP_SESSION session);
  *  @param[in]   fsm              current state machine type (??)
  *  @param[in]   message_type     the type of «@name» message struct to be created (with empty data)
  *
- *  @return      message          the message struct desired
- *  @return      NULL             if the message_type is unknown
+ *  @retval      message          the message struct desired
+ *  @retval      NULL             if the message_type is unknown
  *
- *  @TODO           This description comes entirely from code inspection, but is probably
+ *  @todo           This description comes entirely from code inspection, but is probably
  *                  better optimised by the author. Caveat lector - I may have gotten it wrong.
  */
 «@name»_t *new_«@name»_message(«@name»_PR fsm, int message_type);
@@ -123,7 +123,7 @@ void free_«@name»_state(PEP_SESSION session);
  *
  *  @param[in]   msg              the «@name»_t message struct to free
  *
- *  @TODO           This description comes entirely from code inspection, but is probably
+ *  @todo           This description comes entirely from code inspection, but is probably
  *                  better optimised by the author. Caveat lector - I may have gotten it wrong.
  */
 void free_«@name»_message(«@name»_t *msg);
@@ -146,7 +146,7 @@ void free_«@name»_message(«@name»_t *msg);
  *
  *  @retval         status
  *
- *  @TODO           This description comes entirely from code inspection, but is probably
+ *  @todo           This description comes entirely from code inspection, but is probably
  *                  better optimised by the author. Caveat lector - I may have gotten it wrong.
  *
  */
@@ -165,7 +165,7 @@ PEP_STATUS update_«@name»_state(PEP_SESSION session, «@name»_t *msg,
  *
  *  @retval         status
  *
- *  @TODO           This description comes entirely from code inspection, but is probably
+ *  @todo           This description comes entirely from code inspection, but is probably
  *                  better optimised by the author. Caveat lector - I may have gotten it wrong.
  */
 PEP_STATUS update_«@name»_message(PEP_SESSION session, «@name»_t *msg);

codegen/gen_statemachine.ysl2

@@ -1271,7 +1271,7 @@ tstylesheet {
      *  @param[in]      state       current state
      *
      *  @retval         true        if wait has exceeded «yml:ucase(@name)»_THRESHOLD
-     *                  false       otherwise
+     *  @retval         false       otherwise
      */
     static bool _«@name»_timeout(int state)
     {
@@ -1502,7 +1502,7 @@ tstylesheet {
          *  @param[in]      state       state to convert to string
          *
          *  @retval         string      representation of state name
-         *                  NULL        if invalid state
+         *  @retval         NULL        if invalid state
          */
         const char *«@name»_state_name(int state);
         /**
@@ -1513,7 +1513,7 @@ tstylesheet {
          *  @param[in]      event       event to convert to string
          *
          *  @retval         string      representation of event name
-         *                  NULL        if invalid event
+         *  @retval         NULL        if invalid event
          */
         const char *«@name»_event_name(int event);
         #endif
@@ -1618,7 +1618,7 @@ tstylesheet {
          *                              false for decimal
          *
          *  @retval         string      representation of input
-         *                  NULL        if out of memory or input invalid
+         *  @retval         NULL        if out of memory or input invalid
          */
         static char *_str(int n, bool hex)
         {