Log message:
Drop superfluous PKG_DESTDIR_SUPPORT, "user-destdir" is default these days.
Mark packages that don't or might probably not have staged installation.

Log message:
Import symbolic++-3.35 as wip/symbolic++.

SymbolicC++ uses C++ and object-oriented programming to develop a computer
algebra system. Object-oriented programming is an approach to software design
that is based on classes rather than procedures. This approach maximizes
modularity and information hiding. Object-oriented design provides many
advantages. For example, it combines both the data and the functions that
operate on that data into a single unit. Such a unit
(abstract data type) is called a class.