Warn about functions that are `@disable` but have an function body

[Mai-Lapyst]

D-Scanner should warn about functions that have the @disable annotation but also have an body, like this:

class C1
{
    @disable this() {}

    @disable doSome() {}
}

References:

• https://github.com/dlang/dmd/pull/15052
• https://issues.dlang.org/show_bug.cgi?id=14854