[mono-api-html] Allow ignoring addition of property setters.
As mentioned in commit
789517f8, I'm trying to compare inter-API level
differences in Mono.Android.dll, and want to reduce as much
"meaningless noise" as possible -- changes which don't meaningfully
break API or ABI.
Among those "meaningless" changes are the addition of property setters
to properties. Adding a setter doesn't break API or ABI.
Add a `mono-api-html --ignore-changes-property-setters` option.
--ignore-changes-property-setters:
Ignore the addition of property setters.
If a source property contains a getter and the target property
contains both a getter and a setter, do not flag this as a
change.