* build-aux/export.make: export DESTDIR. * install.sh: Support $DESTDIR.
* build-aux/export.make: New file. * GNUmakefile (man): New target. (doc): Depend on man. include build-aux/export.make, remove exports. * guix.scm (mes): Add dependency on help2man. * configure: Check for help2man. * install.sh: Install manual pages if built.