Bug#35180841 Remove requirement for md5_hash() input to be 8-byte aligned

Addendum patch to silence compiler warning caused by this patch, which
is even treated as a compiler errors on some Pb2 targets - depending on
build configs.

Warning:

  Ndb.cpp:568:11: warning: ‘buf’ may be used uninitialized

Fix is a require() which checks that md5_hash will not access 'buf'
beyond its max size 'bufLen'. As require() is also a 'no return',
compiler will realize that md5_hash() is never reached if reuired does
not hold.

Note that same pattern is also used for another similar md5_hash()
call a few hundred lines further down.

Change-Id: I54b47a0ed59f0926701dc860f1a66943281c0f9d

Author: Ole John Aske

storage/ndb/src/ndbapi/Ndb.cpp

@@ -563,6 +563,8 @@ Ndb::computeHash(Uint32 *retval,
     }
   }
   len = Uint32(UintPtr(pos) - UintPtr(buf));
+  assert((len & 3) == 0);
+  require(len <= bufLen);
 
   Uint32 values[4];
   md5_hash(values, (const char*)buf, len);