Dropping USE_DESTDIR=full

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

Hi all,
unless there are objections, I will drop the distinction between
USE_DESTDIR=yes and USE_DESTDIR=full on Monday, making the latter
the only choice in behavior. That is, only USE_DESTDIR=yes and
USE_DESTDIR=no will exist. Whether or not full destdir support is used
will only depend on the package.

Joerg