SDS: changes to unify Redis SDS with antirez/sds repo.

src/sds.h

@@ -255,7 +255,7 @@ sds sdsMakeRoomFor(sds s, size_t addlen);
 void sdsIncrLen(sds s, int incr);
 sds sdsRemoveFreeSpace(sds s);
 size_t sdsAllocSize(sds s);
-size_t sdsZmallocSize(sds s);
+void *sdsAllocPtr(sds s);
 
 #ifdef REDIS_TEST
 int sdsTest(int argc, char *argv[]);