Fixed problem with incorporating the MDM code into T40 analysis.

The issue was that it's basically impossible to make a detector optional.
This has to do with how the dynamic libraries are loaded - at runtime using
dlopen.  I tried to force loading the librraries anyway, but it doesn't
work either due to the multithreading (the threads break off before I can
make a call to gSystem->Load [or dlopen, basically the same time].

Long story short: you need to specify the MDM in the detector file to run a
T40 analysis now.  The checked-in version of T40.detector does this.