Avoid integer overflow on platforms with 32bit suseconds_t.

At work in Sweden we often fika (coffee+buns and what have u) at 3PM. I sometimes accidentally give a start time of 'teatime', so when I return from 'fika' I see my job's just getting started. This fix should make life even easier for the Swedes.

Logs for jobs which are explicitly requeued will say so rather than saying
that a node in their allocation failed.

This is a minor change to commit 4b8cdd4c
from yesterday and is needed to work with launch/poe (which was
broken by the commit).

--export=NONE is not supported, but --export=name=value is supported.

Conflicts:
	src/slurmctld/reservation.c

a reservation.

which they have access to (rather then preventing them from seeing ANY
reservation).  Backport from 14.11 commit 77c2bd25.

arbitrary layouts (test1.59).

option (since it isn't).

If job or step request a gres count of zero, do not test that the
gres name is valid (e.g. "--gres=foo:0" is fine even if "goo" is
not a valid gres).

Replace putenv() with setenv() to eliminate last CLANG error reported.
setenv makes its own copies of the name/value.