* Update globalmenu-extension code to 1.0 - Fix LP: #755701 - When iterating over each label, check if the current character equals the access key (to set a flag indicating we've already seen it) *before* we mangle the label, rather than after it. This fixes an issue where we never set the flag, and subsequently see the mnemonics repeated multiple times in labels - Also remove the hack we had to add placeholder entries to empty menus so that we could get an about-to-show signal (now that LP: #619811 is fixed)