Fix style in toxav.c.

* Use Camel_Snake_Case for type names.
* Use at least 4 characters for constant names. I.e. `END` is a type
  name, but `RETURN` is a constant name. This is because `DHT` is a type
  name (yay consistency).
* Using `min_*` functions instead of MIN, we can avoid a cast.
* Use `for`-loops for for-each-frame semantics instead of `while`.
* Don't use assignments as expressions.
* `++i` instead of `i++`.
* Function pointers are dereferenced automatically, so no need to
  manually do so.
* Avoid void pointers that lie about not being spaghetti code. Toxcore
  and toxav are both spaghetti and shouldn't pretend anything else.
* Don't use empty statements (e.g. no `;;` anywhere in the code).

toxav/toxav.api.h

@@ -616,8 +616,9 @@ namespace video {
  *
  * Note that total size of pcm in bytes is equal to (samples * channels * sizeof(int16_t)).
  */
-int toxav_add_av_groupchat(Tox *tox, void (*audio_callback)(void *, uint32_t, uint32_t, const int16_t *, unsigned int, uint8_t,
-                           uint32_t, void *), void *userdata);
+int toxav_add_av_groupchat(Tox *tox,
+                           void (*audio_callback)(void *, uint32_t, uint32_t, const int16_t *, unsigned int, uint8_t, uint32_t, void *),
+                           void *userdata);
 
 /* Join a AV group (you need to have been invited first.)
  *
@@ -630,7 +631,8 @@ int toxav_add_av_groupchat(Tox *tox, void (*audio_callback)(void *, uint32_t, ui
  * Note that total size of pcm in bytes is equal to (samples * channels * sizeof(int16_t)).
  */
 int toxav_join_av_groupchat(Tox *tox, uint32_t friendnumber, const uint8_t *data, uint16_t length,
-                            void (*audio_callback)(void *, uint32_t, uint32_t, const int16_t *, unsigned int, uint8_t, uint32_t, void *), void *userdata);
+                            void (*audio_callback)(void *, uint32_t, uint32_t, const int16_t *, unsigned int, uint8_t, uint32_t, void *),
+                            void *userdata);
 
 /* Send audio to the group chat.
  *
@@ -651,5 +653,16 @@ int toxav_group_send_audio(Tox *tox, uint32_t groupnumber, const int16_t *pcm, u
 #ifdef __cplusplus
 }
 #endif
+
+typedef void toxav_group_audio_cb(Tox *tox, uint32_t groupnumber, uint32_t peernumber, const int16_t *pcm, uint32_t samples, uint8_t channels, uint32_t sample_rate, void *user_data);
+
+typedef TOXAV_ERR_CALL Toxav_Err_Call;
+typedef TOXAV_ERR_NEW Toxav_Err_New;
+typedef TOXAV_ERR_ANSWER Toxav_Err_Answer;
+typedef TOXAV_ERR_CALL_CONTROL Toxav_Err_Call_Control;
+typedef TOXAV_ERR_BIT_RATE_SET Toxav_Err_Bit_Rate_Set;
+typedef TOXAV_ERR_SEND_FRAME Toxav_Err_Send_Frame;
+typedef TOXAV_CALL_CONTROL Toxav_Call_Control;
+
 #endif /* TOXAV_H */
 %}