This patch fixes a compile error encountered on newer Ubuntu when building Qt 5.9.7. The issue was observed on Ubuntu 21.10 and 22.04, where a missing include caused compile errors.
This patch just fixes the error by including <limits>.
See BCHN issue #417
This is a backport of https://gitlab.com/bitcoin-cash-node/bitcoin-cash-node/-/merge_requests/1530
Note: the error fixed by this is also seen when compiling Qt 5.12.10 and Qt 5.12.11
It can be dropped with Qt 5.15.x