for std::thread, change reference args to pointers

I ran into an error "...error: no type named 'type' in class std::result_of..."
Google led me to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57716
and I eliminated the error by changing references to pointers as described at
http://stackoverflow.com/questions/15235885/invalid-initialization-of-non-const-reference-with-c11-thread
Simplified Locking in MultList

This was done by moving the mutex from EntList to MultList.