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 gappa-0.12.3 as wip/gappa.

Gappa is a tool intended to help verifying and formally proving properties
on numerical programs dealing with floating-point or fixed-point arithmetic.
It has been used to write robust floating-point filters for CGAL and it is
used to certify elementary functions in CRlibm. While Gappa is intended to
be used directly, it can also act as a backend prover for the Why software
verification plateform or as an automatic tactic for the Coq proof assistant