[Halld-offline] Cleanup of warnings from nightly build

[Simon Taylor]

Hi, everyone.

I am starting to work on cleaning up some of the long list of warnings 
we see in the nightly builds. In particular, we are getting many 
warnings due to the genpi code under programs/Simulation/genpi.   Is 
anybody currently using this particular code?  If not, I will move this 
into the list of optional code to build.

Simon