Edit on matlab memory test 

I have made a very small change,

- In batch import mode, this does not throw out the same warning again and again. 
i.e,The first iteration alone will throw out the warning message. Thereafter there will be no warning messages.
- Saves a warninglog.txt file in the matlab current directory, as a one time warning message. 

Just a small suggestion to improve redundant warnings.

cc/, @sbesson