Makefile.PL: handle PREFIX consistently

Makefile.PL: handle PREFIX consistently

This patch fixes the handling of the PREFIX variable in the generated
Makefile.  The following issues are addressed:

 * drop explicit PREFIX in WriteMakefile call

   By default, the local $Config{prefix} setting should be fine.
   This allows to specify either PREFIX or INSTALL_BASE as Makefile.PL
   parameter, depending on the user needs.

 * use PREFIX in extra_install target

   Previously, pristine-tar, pristine-gz, pristine-bz2, pristine-xz, and
   zgz were always installed to /usr/bin (if $DESTDIR was not set). Also,
   the man pages were always installed to /usr/share/man/man1.

 * call $(MAKE) and pass PREFIX to the build of suse-bzip2

   Although PREFIX is not really used during the build of suse-bzip2,
   it should be passed to the build to enable e.g. the inclusion
   of the "correct" location during the linking process.

Reported-by: Torsten Maehne <torsten.maehne@gmx.de>
Signed-off-by: Philipp A. Hartmann <philipp.hartmann@offis.de>