This fixes an issue where opening a FileTreeComponent could cause the UI
to hang. The call to subcontentsList->isStillLoading() in
FileListTreeItem::selectFile() would always return true because the
file-scanner TimeSliceThread wasn't started until the selectFile() call
finished.

Co-authored-by: Roland Rabien <figbug@gmail.com>

This bug was introduced in 869760cb2a

The previous implementation would trigger assertions in
grabKeyboardFocus() when the DragImageComponent was hidden due to the
target returning false from shouldDrawDragImageWhenOver().

Hiding the image would also mean that its keyboard focus was lost. Now
focus is restored when the image becomes visible again.

The warnings are only silenced in code that is conditionally used on
older platforms. When the newer (non-deprecated) API is available, it
will be used.

The current minimum-supported Xcode (10.1) includes the macOS 10.14.1
SDK, so APIs from macOS 10.14 will always be available.

The current minimum-supported Xcode (10.1) includes the macOS 10.14.1
SDK, so APIs from macOS 10.13 will always be available.

The current minimum-supported Xcode (10.1) includes the macOS 10.14.1
SDK, so APIs from macOS 10.12 will always be available.

The current minimum-supported Xcode (10.1) includes the iOS 12.1 SDK, so
APIs from iOS 12 will always be available.

The current minimum-supported Xcode (10.1) includes the iOS 12.1 SDK, so
APIs from iOS 10 will always be available.

The current minimum-supported Xcode (10.1) includes the iOS 12.1 SDK, so
APIs from iOS 10 will always be available.

Prior to this commit it was possible to get the menu bar deactivated
by moving the mouse to an adjacent menu item and then back again. If
the movement was quick enough the corresponding PopupMenu would be
dismissed and created again before the dismissal's async command
handler would run. The command handler would see that the dismissed
menu's index and the currently activated index are equal and
deactivate the menu bar.

Previously having a JUCE title bar prevented the style flags from
being restored, and this caused the native window border resizers to
remain active after entering and then leaving full screen.

This provides an improved user experience, allowing cursor movement
directly from the keyboard.

- Fixes an off-by-one error when navigating by rows, caused by treating
  the table header as a row. The table header now has the header
  accessibility role.
- Fixes a bug where reordering table columns would cause the table to
  become inaccessible.
- Fixes a bug where the screen reader would try to navigate hidden table
  columns.
- Fixes an issue where moving the VoiceOver cursor to a partially hidden
  cell would cause the focus to move to the table itself, rather than to
  the cell.

This change avoids a situation where a standalone plugin's Audio/Midi
settings window could appear in a wrong position.

Using this new function a previous bug is avoided where transforms
were applied differently to drawable paths and text elements.