Auto merge of #7065 - rail-rain:warn_copy_pass_by_ref, r=Manishearth
Auto merge of #7065 - rail-rain:warn_copy_pass_by_ref, r=Manishearth

Add a note on the issue #5953

Hello,

I thought it would be better to have a note and warning about this issue considering it introduced an UB in the past even with the "Search on Github" feature.

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changelog: Add a note on the issue #5953 to the known problems section.

aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust