Export more symbols to fix the mpd module

All of the newly exported symbols seemed to make sense as exports, so I
added them to the EXPORT form of their respective files.
Add optional EXTRA-KEYMAP argument to SELECT-FROM-MENU

This removes the need for rebinding *MENU-KEYMAP* and thus allows for
easier adding of keybindings to a menu.
Merge pull request #95 from jorams/export-symbols-for-mpd

Export more symbols to fix the mpd module