Split MESSAGE->flags field into author and msg_type

Previously it consisted of authorship bit in the
lowest position, followed by a couple of bits indicating
one of 4 message types (text, action, image, file).

This led to more magic numbers, bit twiddling,
and arithmetic hacks, than is reasonable by any measure.

Since MESSAGE struct doesn't seem to be
format-restricted (e.g. on-disk format), this field
is removed and replaced with two straightforward ones,
and the 4 types are properly encoded as an enum.

Additionally TOX_FILE_OUT_PAUSE & Co. are now referred
directly instead of arithmetically too.

The end result is cleaner code and some comparison/signedness
warnings fixed.

friend.c

@@ -4,7 +4,8 @@ void friend_setname(FRIEND *f, char_t *name, STRING_IDX length)
 {
     if(f->name && (length != f->name_length || memcmp(f->name, name, length) != 0)) {
         MESSAGE *msg = malloc(sizeof(MESSAGE) + sizeof(" is now known as ") - 1 + f->name_length + length);
-        msg->flags = 2;
+        msg->author = 0;
+        msg->msg_type = MSG_TYPE_ACTION_TEXT;
         msg->length = sizeof(" is now known as ") - 1 + f->name_length + length;
         char_t *p = msg->msg;
         memcpy(p, f->name, f->name_length); p += f->name_length;
@@ -30,7 +31,8 @@ void friend_setname(FRIEND *f, char_t *name, STRING_IDX length)
 void friend_sendimage(FRIEND *f, void *data, void *pngdata, uint16_t width, uint16_t height)
 {
     MSG_IMG *msg = malloc(sizeof(MSG_IMG));
-    msg->flags = 5;
+    msg->author = 1;
+    msg->msg_type = MSG_TYPE_IMAGE;
     msg->w = width;
     msg->h = height;
     msg->zoom = 0;
@@ -51,7 +53,8 @@ void friend_recvimage(FRIEND *f, void *pngdata, uint32_t size)
     }
 
     MSG_IMG *msg = malloc(sizeof(MSG_IMG));
-    msg->flags = 4;
+    msg->author = 0;
+    msg->msg_type = MSG_TYPE_IMAGE;
     msg->w = width;
     msg->h = height;
     msg->zoom = 0;
@@ -77,7 +80,8 @@ void friend_notify(FRIEND *f, char_t *str, STRING_IDX str_length, char_t *msg, S
 void friend_addmessage_notify(FRIEND *f, char_t *data, STRING_IDX length)
 {
     MESSAGE *msg = malloc(sizeof(MESSAGE) + length);
-    msg->flags = 2;
+    msg->author = 0;
+    msg->msg_type = MSG_TYPE_ACTION_TEXT;
     msg->length = length;
     char_t *p = msg->msg;
     memcpy(p, data, length);
@@ -95,11 +99,15 @@ void friend_addmessage(FRIEND *f, void *data)
 
     message_add(&messages_friend, data, &f->msg);
 
-    if(msg->flags < 4) {
+    switch(msg->msg_type) {
+    case MSG_TYPE_TEXT:
+    case MSG_TYPE_ACTION_TEXT: {
         char_t m[msg->length + 1];
         memcpy(m, msg->msg, msg->length);
         m[msg->length] = 0;
         notify(f->name, f->name_length, m, msg->length);
+        break;
+    }
     }
 
     if(sitem->data != f) {
@@ -154,11 +162,13 @@ void friend_free(FRIEND *f)
     MSG_IDX i = 0;
     while(i < f->msg.n) {
         MESSAGE *msg = f->msg.data[i];
-        if((msg->flags & (~1)) == 4) {
+        switch(msg->msg_type) {
+        case MSG_TYPE_IMAGE: {
             //MSG_IMG *img = (void*)msg;
             //todo: free image
+            break;
         }
-        if((msg->flags & (~1)) == 6) {
+        case MSG_TYPE_FILE: {
             MSG_FILE *file = (void*)msg;
             free(file->path);
             FILE_T *ft = &f->incoming[file->filenumber];
@@ -171,9 +181,11 @@ void friend_free(FRIEND *f)
                 }
             }
 
-            if(msg->flags & 1) {
+            if(msg->author) {
                 ft->status = FT_NONE;
             }
+            break;
+        }
         }
         message_free(msg);
         i++;