Rollup merge of #22862 - vhbit:broken-open, r=alexcrichton

 According to Apple's [arm64 calling convention](https://developer.apple.com/library/ios/documentation/Xcode/Conceptual/iPhoneOSABIReference/Articles/ARM64FunctionCallingConventions.html#//apple_ref/doc/uid/TP40013702-SW1) varargs always are passed
through stack. Since `open` is actually a vararg function on Darwin,
it means that older declaration caused permissions to be taken from
stack, while passed through register => it set file permissions
to garbage and it was simply impossible to read/delete files after they
were created.

They way this commit handles it is to preserve compatibility with
existing code - it simply creates a shim unsafe function so all existing
callers continue work as nothing happened.

0 files changed, 0 insertions, 0 deletions