Add support of RESP3 attribute type

Currently, Redis DEBUG PROTOCOL 'attrib' command will return an
attribute type, but hiredis doesn't support it yet. So it got the
protocol type error:

```
127.0.0.1:6379>  DEBUG PROTOCOL attrib
Error: Protocol error, got "|" as reply type byte
```

After apply this PR, it should reply:

```
127.0.0.1:6379> DEBUG PROTOCOL attrib
1# "key-popularity"
1# 1) "key:123"
   2) (integer) 90
```

hiredis.c

@@ -102,6 +102,7 @@ void freeReplyObject(void *reply) {
         break; /* Nothing to free */
     case REDIS_REPLY_ARRAY:
     case REDIS_REPLY_MAP:
+    case REDIS_REPLY_ATTR:
     case REDIS_REPLY_SET:
     case REDIS_REPLY_PUSH:
         if (r->element != NULL) {
@@ -160,6 +161,7 @@ static void *createStringObject(const redisReadTask *task, char *str, size_t len
         parent = task->parent->obj;
         assert(parent->type == REDIS_REPLY_ARRAY ||
                parent->type == REDIS_REPLY_MAP ||
+               parent->type == REDIS_REPLY_ATTR ||
                parent->type == REDIS_REPLY_SET ||
                parent->type == REDIS_REPLY_PUSH);
         parent->element[task->idx] = r;
@@ -192,6 +194,7 @@ static void *createArrayObject(const redisReadTask *task, size_t elements) {
         parent = task->parent->obj;
         assert(parent->type == REDIS_REPLY_ARRAY ||
                parent->type == REDIS_REPLY_MAP ||
+               parent->type == REDIS_REPLY_ATTR ||
                parent->type == REDIS_REPLY_SET ||
                parent->type == REDIS_REPLY_PUSH);
         parent->element[task->idx] = r;
@@ -212,6 +215,8 @@ static void *createIntegerObject(const redisReadTask *task, long long value) {
         parent = task->parent->obj;
         assert(parent->type == REDIS_REPLY_ARRAY ||
                parent->type == REDIS_REPLY_MAP ||
+               parent->type == REDIS_REPLY_ATTR ||
+               parent->type == REDIS_REPLY_SET ||
                parent->type == REDIS_REPLY_SET ||
                parent->type == REDIS_REPLY_PUSH);
         parent->element[task->idx] = r;
@@ -249,6 +254,7 @@ static void *createDoubleObject(const redisReadTask *task, double value, char *s
         parent = task->parent->obj;
         assert(parent->type == REDIS_REPLY_ARRAY ||
                parent->type == REDIS_REPLY_MAP ||
+               parent->type == REDIS_REPLY_ATTR ||
                parent->type == REDIS_REPLY_SET ||
                parent->type == REDIS_REPLY_PUSH);
         parent->element[task->idx] = r;
@@ -267,6 +273,7 @@ static void *createNilObject(const redisReadTask *task) {
         parent = task->parent->obj;
         assert(parent->type == REDIS_REPLY_ARRAY ||
                parent->type == REDIS_REPLY_MAP ||
+               parent->type == REDIS_REPLY_ATTR ||
                parent->type == REDIS_REPLY_SET ||
                parent->type == REDIS_REPLY_PUSH);
         parent->element[task->idx] = r;
@@ -287,6 +294,7 @@ static void *createBoolObject(const redisReadTask *task, int bval) {
         parent = task->parent->obj;
         assert(parent->type == REDIS_REPLY_ARRAY ||
                parent->type == REDIS_REPLY_MAP ||
+               parent->type == REDIS_REPLY_ATTR ||
                parent->type == REDIS_REPLY_SET ||
                parent->type == REDIS_REPLY_PUSH);
         parent->element[task->idx] = r;

read.c

@@ -250,6 +250,7 @@ static void moveToNextTask(redisReader *r) {
         prv = r->task[r->ridx-1];
         assert(prv->type == REDIS_REPLY_ARRAY ||
                prv->type == REDIS_REPLY_MAP ||
+               prv->type == REDIS_REPLY_ATTR ||
                prv->type == REDIS_REPLY_SET ||
                prv->type == REDIS_REPLY_PUSH);
         if (cur->idx == prv->elements-1) {
@@ -534,7 +535,7 @@ static int processAggregateItem(redisReader *r) {
 
             moveToNextTask(r);
         } else {
-            if (cur->type == REDIS_REPLY_MAP) elements *= 2;
+            if (cur->type == REDIS_REPLY_MAP || cur->type == REDIS_REPLY_ATTR) elements *= 2;
 
             if (r->fn && r->fn->createArray)
                 obj = r->fn->createArray(cur,elements);
@@ -602,6 +603,9 @@ static int processItem(redisReader *r) {
             case '%':
                 cur->type = REDIS_REPLY_MAP;
                 break;
+            case '|':
+                cur->type = REDIS_REPLY_ATTR;
+                break;
             case '~':
                 cur->type = REDIS_REPLY_SET;
                 break;
@@ -642,6 +646,7 @@ static int processItem(redisReader *r) {
         return processBulkItem(r);
     case REDIS_REPLY_ARRAY:
     case REDIS_REPLY_MAP:
+	case REDIS_REPLY_ATTR:
     case REDIS_REPLY_SET:
     case REDIS_REPLY_PUSH:
         return processAggregateItem(r);

test.c

@@ -795,6 +795,26 @@ static void test_reply_reader(void) {
     freeReplyObject(reply);
     redisReaderFree(reader);
 
+    test("Can parse RESP3 attribute: ");
+    reader = redisReaderCreate();
+    redisReaderFeed(reader, "|2\r\n+foo\r\n:123\r\n+bar\r\n#t\r\n",26);
+    ret = redisReaderGetReply(reader,&reply);
+    test_cond(ret == REDIS_OK &&
+        ((redisReply*)reply)->type == REDIS_REPLY_ATTR &&
+        ((redisReply*)reply)->elements == 4 &&
+        ((redisReply*)reply)->element[0]->type == REDIS_REPLY_STATUS &&
+        ((redisReply*)reply)->element[0]->len == 3 &&
+        !strcmp(((redisReply*)reply)->element[0]->str,"foo") &&
+        ((redisReply*)reply)->element[1]->type == REDIS_REPLY_INTEGER &&
+        ((redisReply*)reply)->element[1]->integer == 123 &&
+        ((redisReply*)reply)->element[2]->type == REDIS_REPLY_STATUS &&
+        ((redisReply*)reply)->element[2]->len == 3 &&
+        !strcmp(((redisReply*)reply)->element[2]->str,"bar") &&
+        ((redisReply*)reply)->element[3]->type == REDIS_REPLY_BOOL &&
+        ((redisReply*)reply)->element[3]->integer);
+    freeReplyObject(reply);
+    redisReaderFree(reader);
+
     test("Can parse RESP3 set: ");
     reader = redisReaderCreate();
     redisReaderFeed(reader, "~5\r\n+orange\r\n$5\r\napple\r\n#f\r\n:100\r\n:999\r\n",40);