Introduced special token LIBO_DEV_INSTALL=TRUE to communicate what install set
to build from Makefile.top's dev-install target to
instsetoo_native/util/makefile.mk.  Somewhat arbitrarily, always use a "release"
install set regardless of --enable-release-build (the dev-install set is used
for "make check," and it is safer to test "release" install sets in
--disable-release-build builds than the other way around, should those builds
ever start to deviate significantly).

The "always build a defaul-laguage openoffice product" logic had been obsoleted
a long time ago already.

Change-Id: I64ec87a0b8dc6fe81cab5531c43e29db3f5128af