Before, it was difficult to edit the R code since all dollars,
backslashes and backticks had to be escaped. Separating the code also
makes the R part testable on its own.
Changes since 0.6:
* Run properly even if TMPDIR is not set.
* Quote variables to prevent unintended interpolation.
* Write error messages to stderr instead of stdout.
Changes since version 0.5:
* Improve the canonical format of an R package Makefile:
- Place R_PKGNAME, R_PKGVER, and CATEGORIES in the first stanza.
- Simplify CATEGORIES by defining common ones in Makefile.extension.
- Use the default value of HOMEPAGE defined in Makefile.extension.
* Annotate generated comments with [R2pkg] to make them easier to find.
Changes since 0.3:
* Fix recursion.
* Add both c and c++ to USE_LANGUAGES.
* Add maintainer email handling (-M).
* Use buildlink3.mk files for dependencies when available.
