add compat use-region-p and use it throughout

git-svn-id: https://svn.r-project.org/ESS/trunk@5714 0bbaf3bd-34e0-0310-bf65-c717079852d4
ess-developer: re-factor

  Also replace ess--developer-containing-package with ess-developer--get-package-name

git-svn-id: https://svn.r-project.org/ESS/trunk@5715 0bbaf3bd-34e0-0310-bf65-c717079852d4