Add method to represent expression transformations as text strings.

Signed-off-by: Rami Ylimäki <rami.ylimaki@vincit.fi>
Apply transformations to initializers of relocated variables.

The default mechanism doesn't transform initializers since we have
commented out the corresponding source location. We need to represent
an intializer twice:
- preserve the original representation in comments
- transform the initializer for generated assignments

Signed-off-by: Rami Ylimäki <rami.ylimaki@vincit.fi>