fix issue 19432 automatically interpret big int literals as

[benjones]

unsigned longs if they don't fit in a signed long.

I made a corresponding PR for dlang.org, but I don't know the best way to PRs

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19432	normal	Cannot initialize ulong with decimal value above signed long range

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + dmd#10607"