Restored env parameter to .ddg.create.data.node.for.possible.writes.

Changed calls to .ddg.link.function.returns to pass in the string
version of the command, not the parsed command.
Changed code to avoid duplicate node creation when executing ddg.eval
when running a script with ddg.source.
Fixed problem with not finding return statements due to differences in
spacing between original text and deparsed value stored in the returns
table.

Fixed problem with duplicate start, finish and data nodes when
ddg.source is used, calls ddg.eval, which in turn calls a function that
is annotated with ddg.function.
Removed .ddg.in.ddg.eval variable since it is not needed to solve the
ddg.source -- ddg.eval problem.
Updated version number, cleaned up library, added Eval2Test to test
suite.