[Emacspeak] Bug in auditory icon theme definition

[Tim Cross <theophilusx@xxxxxxxxxxx>]

Found this issue while chasing down some other issues relating to
playing of auditory icons. Seems there may be a bug in
emacspeak-sounds-select-theme. After selecting a theme, even the
existing default theme, the error "Icon <name> not defined" errors are
generated.

This is a low priority bug as it won't affect anyone unless they try to
change the icon theme.

To reproduce -

- Start Emacs and load Emacspeak.
- Run emacspeak-sounds-select-theme, either via M-x or C-e ).
- Select a theme. pan-chimes (the defualt).
- Do a find file or some other operation which would normally cause the
  playing of open-object icon. Error generated "Icon opoen-object not
  defined".

Note that the error is not generated when you start emacs and before
running emacspeak-sounds-select-theme. Errors occur regardless of which
theme you select, including selecting the same theme loaded by default
when emacs starts. This likely indicates that the theme itself is
complete, but a mapping is missing when emacspeak-sounds-select-theme
resets the theme. 

I confirmed this issue with both the current master head and with the
code as it was when v57 was released 13 days ago.