Add minor improvements to psi2ir and IR utilities:

* Generate missing IR parameter declarations in external stubs
* Use origin = FAKE_OVERRIDE in external IR stubs for fake overrides
* Set .parent in external IR stubs
* Set .parent in IR generated by some utility methods

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/ir/IrUtils.kt

@@ -113,6 +113,7 @@ fun IrClass.addSimpleDelegatingConstructor(superConstructorSymbol: IrConstructor
                 )
         )
 
+        constructor.parent = this
         this.declarations.add(constructor)
     }
 }

compiler/ir/backend.common/src/org/jetbrains/kotlin/ir/util/IrUtils.kt

@@ -126,7 +126,9 @@ fun IrFunction.createParameterDeclarations() {
             innerStartOffset(this), innerEndOffset(this),
             IrDeclarationOrigin.DEFINED,
             this
-    )
+    ).also {
+        it.parent = this@createParameterDeclarations
+    }
 
     dispatchReceiverParameter = descriptor.dispatchReceiverParameter?.irValueParameter()
     extensionReceiverParameter = descriptor.extensionReceiverParameter?.irValueParameter()
@@ -140,7 +142,9 @@ fun IrFunction.createParameterDeclarations() {
                 innerStartOffset(it), innerEndOffset(it),
                 IrDeclarationOrigin.DEFINED,
                 it
-        )
+        ).also { typeParameter ->
+            typeParameter.parent = this
+        }
     }
 }