Added nothrow @nogc @safe to the allocate function.

[George-Alex-Berea]

Also added these flags to all the functons it calls.
In order to make the functions safe I isolated the 'unsafe' parts inside @trusted lambda expressions, inspired by edi33416's pull request #6416.
Additionally, added nothrow @nogc @safe to the allocateAll function, since it only calls allocate.

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[teodutu]

@edi33416 if you remember any of this from ages ago, please add your review as it revives your work.

[George-Alex-Berea]

@andralex can you please take a look?

[andralex]

looking good!

[George-Alex-Berea]

Should something more be done to get this PR merged?

[thewilsonator]

No, I just need to take a good close look at those @trusted functions

[George-Alex-Berea]

Ok, thanks!

[thewilsonator]

CC @teodutu please re-review

[teodutu]

It's looking fine now. Thanks @George-Alex-Berea.