if joining file check if XXX.000 is just splitter info, if yes skip it

When file is split with software like MasterSplitter , filename.000 is just info,  we have to skip it , if not merge file is corrupted ( unreadable wmv movie file for example ).

usually filename.000 created just for info is quite small , so if size is < 1kb we are skipping it.

this commit correct the problem for me , no regression found

tested with python 2.7.5 on fedora linux fc19