stream: remove unused gap structure from StreamMsg.

src/stream.h

@@ -43,18 +43,12 @@ typedef struct StreamMsg_ {
     struct StreamMsg_ *next;
     struct StreamMsg_ *prev;
 
-    union {
-        /* case !STREAM_EOF && !STREAM_GAP */
-        struct {
-            uint32_t seq;               /**< sequence number */
-            uint32_t data_len;          /**< length of the data */
-            uint8_t data[MSG_DATA_SIZE];/**< reassembled data */
-        } data;
-        /* case STREAM_GAP */
-        struct {
-            uint32_t gap_size;
-        } gap;
-    };
+    /* case !STREAM_EOF && !STREAM_GAP */
+    struct {
+        uint32_t seq;               /**< sequence number */
+        uint32_t data_len;          /**< length of the data */
+        uint8_t data[MSG_DATA_SIZE];/**< reassembled data */
+    } data;
 
 } StreamMsg;