Document IgnoresAccessChecksToAttribute

[GSPP]

The IgnoresAccessChecksToAttribute attribute appears to be not documented on MSDN and not even defined in the base class libraries.

Is it supported? If yes, it should be documented and defined out of the box. If no, well, according to my research it has found usage and there is unofficial documentation. This is not a great state to be in.

[davidwrighton]

This api is not supported. It was built for internal runtime team support, and not intended for use outside of special purpose build logic. In addition, there are no tests, or spec for the attribute, and the mono runtime does not support the attribute.

[dubiousconst282]

This might be a little stretched, but is there a reason for the runtime to even enforce access rules nowadays? I can't see how it provides meaningfulness since access checks can be readily bypassed using reflection and unsafe ref trickery.

In either way, I believe that documenting IACT would be very helpful for IL rewriting/optimization tools, as it already allows for transforms such as inlining to be significantly more effective (at least functionality-wise).