TypeDoc incorrectly marks properties with more than one source as overridden

[Gerrit0]

Surely there's a better title... I ran into this while investigating #642, where the stack property on a custom Error type will show up as overridden since it is defined both in lib.es5.d.ts and globals.d.ts (from @types/node)

• I have checked issues with bug label and found no duplicates

Expected Behavior

Given the following code, the stack property should show up under B as inherited from A, but not as overridden from A.

interface A {
    stack?: string
}
class A {
    stack?: string
}
class B extends A {}

Actual Behavior

Environment

• Typedoc version: master
• Node.js version: 12.x
• OS: Windows

[Gerrit0]

This should probably be addressed when fixing #1191

[Gerrit0]

This works in 0.20.4