#11 Man page installation disregards DESTDIR

[Göran Uddeborg]

When doing an installation using DESTDIR, make still attempts to install the manual page directly in /usr/share/man. I suggest this patch to Makefile.in:

- $(INSTALL) xgalaga.6x.gz $(mandir)/man6/xgalaga.6x.gz
+ $(INSTALL) xgalaga.6x.gz $(DESTDIR)$(mandir)/man6/xgalaga.6x.gz