Issue 14909: Provided a fix for the forward range version of chunkBy …

[jamesragray]

…so that it can accept predicates reference variables in the calling function. Sorry about creating a second pull request but I was having problems with git.

[dlang-bot]

Thanks for your pull request and interest in making D better, @jamesragray! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✗	14909	normal	Template argument of std.algorithm.iteration.chunkBy cannot access a local variable

Testing this PR locally

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

dub run digger -- build "master + phobos#7625"