#235 Disable or hide empty top-level menus (Mac)

[David A. Mellis]

Some of the top-level menus are sometimes empty (e.g.
the Edit and Views menus when the Explorer has the
focus). Disable or hide these menus rather than
allowing the user to click them only to discover that
they're empty.

Boa Constructor 0.4 on Mac OS X with wxPython 2.5.4.1.