`transmute_undefined_repr` fix

[Jarcho]

changelog: Don't lint transmute_undefined_repr when the the first field of a repr(C) type is compatible with the other type

[rust-highfive]

r? @xFrednet

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[xFrednet]

Could you have a look at the CI? Then we can merge this :)

[Jarcho]

The most recent change allows casts between *const/mut int_type and any type as a form of type erasure. *u8/i8 are used as an untyped buffer. I've also seen *u16/i16 used due to windows api's counting by them.

[xFrednet]

Looks good to me, thank you for the update!

@bors r+

[bors]

:pushpin: Commit 99e77d07b2856fccd083d5810a9756e07cc4c524 has been approved by xFrednet

It is now in the queue for this repository.

[bors]

:hourglass: Testing commit 99e77d07b2856fccd083d5810a9756e07cc4c524 with merge 84fb7e039565ac87f504af235940a568b90e7223...

[bors]

:sunny: Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test Approved by: xFrednet Pushing 84fb7e039565ac87f504af235940a568b90e7223 to master...