[Halld-offline] Changes to mcsmear and cdc-related code

[Simon Taylor]

Hi, offliners.

I have just committed some changes to mcsmear to allow dropping of the 
Truth Hits from the output file.  The Truth Hits stored the results 
generated by HDGeant, which are then smeared by the mcsmear code.  To 
turn on this option, use the -d command-line flag.   By default this 
behavior is currently turned off, so without the -d flag, the output 
file will contain both xxxHit and xxxTruthHit entries.

In order to implement this scheme I had to make some changes in the HDDM 
library in DEventSourceHDDM.cc.

Finally, I have made a small change in the event.xml file in the HDDM 
directory to change the name of the cdc straw hit variable dE to q to 
reflect what is actually being generated by HDGeant.  This means that 
hitCDC.c in HDGeant and libraries/CDC need to updated.

Please let me know if you experience problems related to these changes.

Simon