Eliminate a couple of compile warnings produced when DEF_PAGER is
defined: unixmain.c: g.catmore=DEF_PAGER; wintty.c: fd=open(...).
Override its use when DLB is also defined since an external pager
could access 'license' but not 'history', 'opthelp', &c when those
are in the dlb container file.
In the commented out value for DEF_PAGER, show a viable value for
the default configuration these days.
ccfddd47de