Allow specifying separate symbol names and plugin names.
Add file for popgen builtins.
Define builtins in PopGen.hs, remove from popgen.C.
Update test9.hs.
Add new builtin to PopGen module.
Add ** power function to prelude.
Add code for new builtin.
Make bernoulli default to False.
Switch popgen.C to use OVector.
Define the afs2 distribution.
Add a new test for the diploid sampling chain.