DUMP implemented, RESTORE and MIGRATE fixed. Use zcalloc() instead of zmalloc()+memset() in sds.c when a new string is created with NULL initialization pointer.

src/redis.h

@@ -1180,6 +1180,7 @@ void unwatchCommand(redisClient *c);
 void clusterCommand(redisClient *c);
 void restoreCommand(redisClient *c);
 void migrateCommand(redisClient *c);
+void dumpCommand(redisClient *c);
 
 #if defined(__GNUC__)
 void *calloc(size_t count, size_t size) __attribute__ ((deprecated));