Breaking documentation changes

First, short explanation about what a stability guarantee is: a statement in the document which explains what the item is doing in a precise case. For example:

• Showing precisely how a function on floats handles NaN.
• Saying that a sort method has a particular running-time bound.

So if a doc change updates/adds/removes a stability guarantee, it has to be very carefully handled and needs to go through the libs API team FCP.

It can be circumvented by adding a # Current Implementation section like done here.