core: update WeeChat logo in debian/weechat.xpm
core: update man page and add translations (in french, german, italian, and japanese)
core: add dependencies docbook-xml and docbook-xsl in debian/control
core: fix wrong spaces in italian translations for irc part/quit messages
core: remove obsolete command line option -k/--keys

The user's guide is better to view WeeChat default keys.