core: display error number and string in some network errors

Error number and string is now displayed when an error is returned by one of
these functions: socket, setsockopt, fcntl, pipe, accept, bind, listen, mkfifo.
core: sync debian files with debian git repository
Merge branch 'master' of git://git.sv.gnu.org/weechat

Conflicts:
	po/ja.po
translation: update
Merge branch 'master' of git://git.sv.gnu.org/weechat
translation: update