fbbff63f2e
WithLimit ignored a zero limit, so /v1/entries?limit=0 produced a query
without a SQL LIMIT and returned every matching entry, bypassing the
1000-entry cap. The official API client sends limit=0 for any filter
with an unset Limit field, making unbounded queries easy to trigger.
Clamp non-positive values to the maximum in both WithLimit and
WithLimitAndMaximum so every caller (REST API, Google Reader) stays
bounded, as intended by 0909323a.