GHC events as a profiling tool.

Configuration module now has 'event' function that permits tracing times of some IO actions in ghc eventlog.

Cabal file modified accordingly.

There are now eventlog traces in main module.

Also add of start-ddp-SIMD-eventlog as an example of how to run programs. Unfortunately, we have to copy programs to different names to perform reliable logging, otherwise they write to the same .eventlog file. Even symlinks do not work.