[Denemo-devel] Accelerator fixes

[Richard Shann]

I've checked in my fixes for the accelerators because they are hanging
around too long, and they improve the behaviour of the program. Despite
all the help from Jean-Rene I still can't get the latest git, and hence
can't get his latest fixes.
So my awful dialog when you right click on a menu item is still there
but:
1) there is a single path for all keypresses (via
scorearea_keypress_event() in keypresses.c) - no accelerators are used.
2) all shortcuts are shown on the menus not just the one as with
accelerators.

There is still some tidying to do: 
1)The standard.accels is still loaded, it just contains removal of
accelerators that get defined because we use the STOCK_ICONs in
menu_entries[]. The fix is to make copies of these icons and use them as
private icons. (We could, of course, design our own, but I think it is
good to stick with the recognized ones).

2) And, I suspect we may not need any of the accelerator code to be
involved (I am not sure whether JRR's snooper will detect keypresses on
menu items regardless of whether gtk has been told to expect quick
shortcut settings, if not we can simplify the code, which at the moment
sets and then unsets the accelerators straight away).

3) There is some duplicated code.

4) The shortcuts are not flush right, as accelerators are. This could be
tricky to fix, and does not look too bad anyway.

Richard