Feature/pr454 follow up

[eddelbuettel]

This PR contains four commits which

• add missing entries for Module enhancements #454 and Fixing issue with Rcpp::String and Rcpp::Nullable #453, cleans up NEWS a little
• rolls the minor version to 0.12.4.3 following Module enhancements #454
• skip an older unit test for Environments (follow-up in email)
• and renamed the new copy() function to copyObject() as discussed in Module enhancements #454

[romainfrancois]

Thanks. There should be more coming shortly. I want to be able to manipulate references of module objects somehow. I have a pretty decent idea on how this should work.

@eddelbuettel can you add me back as a commiter. I'll only work in branches and let one of you do the merging, but at least it would be easier to work on these branches, i.e. no need for you to create additional branches before you merge ...