Update Claws Mail to its latest version and perform a major refactoring.
Previously, the configurable arguments were neither complete nor named
according to the configure.ac file. Likewise, the values did not
correspond to the defaults, but rather to a personal preference.
This has now been changed to enable the arguments which are enabled in
the configure.ac file. Also the variable names have been adjusted. For
compatibility the old parameters also exist.
Next to the claws-mail package is the "experimental" claws-mail-gtk3
package for the non official gtk3 git branch. This package started as an
almost one-to-one copy of the claws-mail derivation which small
modifications. This package was of course not updated.
This has also been changed so that both packages are built from the same
derivative.