RDB version signature bumped to 2, now that direct saving of specially encoded...

RDB version signature bumped to 2, now that direct saving of specially encoded types is implemented 2.2 instances are no longer able to read rdb files produced by 2.4 or unstable.

src/rdb.c

@@ -425,7 +425,7 @@ int rdbSave(char *filename) {
             strerror(errno));
         return REDIS_ERR;
     }
-    if (fwrite("REDIS0001",9,1,fp) == 0) goto werr;
+    if (fwrite("REDIS0002",9,1,fp) == 0) goto werr;
     for (j = 0; j < server.dbnum; j++) {
         redisDb *db = server.db+j;
         dict *d = db->dict;
@@ -931,7 +931,7 @@ int rdbLoad(char *filename) {
         return REDIS_ERR;
     }
     rdbver = atoi(buf+5);
-    if (rdbver != 1) {
+    if (rdbver < 1 || rdbver > 2) {
         fclose(fp);
         redisLog(REDIS_WARNING,"Can't handle RDB format version %d",rdbver);
         return REDIS_ERR;