Fix bug #1077 with popping new frames from a minibuffer-only frame.

Fix bug #1077 with popping new frames from a minibuffer-only frame.

 menu-bar.el (menu-bar-frame-for-menubar, menu-bar-positive-p):
 New functions.
 (menu-bar-showhide-menu) <menu-bar-mode, showhide-tool-bar>: Use
 them instead of `nil' and `>', respectively.
 (menu-bar-showhide-tool-bar-menu): Use menu-bar-frame-for-menubar
 instead of `nil'.
 (toggle-menu-bar-mode-from-frame): Use menu-bar-frame-for-menubar
 and menu-bar-positive-p instead of `nil' and `>', respectively.