When building for arm64 with a VS generator on a x86_64 host,
CMAKE_CROSSCOMPILING is not set, and copying the generator platform can
result in a juceaide binary that doesn't run on the host system.

The removed code no longer seems to be necessary when configuring with
newer Clion versions.

This patch also updates the MidiDemo to automatically refresh the device
lists when the set of available devices changes.

Previously, for the following snippet, the menu's LnF was incorrectly
being forced to the default LnF. The correct behaviour is to display the
menu using LnF v4. The menu doesn't have an explicit LnF set, so it
should use the LnF of its parent component.

    LookAndFeel::setDefaultLookAndFeel (&lookAndFeel_V1);
    setLookAndFeel (&lookAndFeel_V4);
    PopupMenu().showMenuAsync (PopupMenu::Options{}.withParentComponent (this));

This reverts commit 4deea8ed93.

Previously, all parameter changes were routed first into
cachedParamValues. Then, on each audio callback, an update would be sent
to the editor via the parameterDispatcher for each changed value in
cachedParamValues.

Now, parameter changes are immediately added to the parameterDispatcher,
without needing to wait for an audio callback.

In Windows DLL builds we inject operator new/delete definitions into
classes with a leak detector. This requires that all inheritance from
such classes must be public, and classes inheriting from multiple such
classes must disambiguate between the base's operators.