[Issue 16447] make illegal for functions containing a `naked` asm block to return `auto`

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=16447

Basile-z <b2.temp at gmx.com> changed:

           What    |Removed                     |Added
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            Summary|Warn about auto return type |make illegal for functions
                   |when no return statement is |containing a `naked` asm
                   |present                     |block to return `auto`

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