GetMenuBar
returns handle leading to data of current menu bar
This lets you get a copy of the current menu list, in case you want to install a
different, temporary menu list.
Returns: a generic Handle; a handle leading to a variable-length menu list structure (not formally named or defined) that is a duplicate of the
current menu list.
Notes: This function allocates storage the size of the current menu list, copies its
data, and returns a handle to the copy. Note that this does not copy the
menus themselves; it only duplicates the list of MenuHandles.
When you restore this list later, be sure that all menu handles are still
valid.
up the memory allocated by this call.