move growl notifications to their own file

TODO: in the Xcode projectfile, add -DHAVE_GROWL flags to the
targets

- notifications.cpp
- growl_notification.cpp

Otherwise, when the project compiles growl notifications will not
be enabled.
give a warning when notifications enabled but not available

The "disable notifications" option in advanced preferences allows
the user to toggle desktop notifications on and off. However, if
the game was not compiled with support for these, the option won't
do anything.

In this revision, if disable_notifications is set to false, but
notifications are not available, a dialog is launched which
explains that this executable was not compiled with support for
notifications.

The preference *is* toggled however -- this is because all versions
of wesnoth use the same preference file (at least under linux), so
we would rather to allow the user to change the file at will --
a different wesnoth binary which they have may indeed support
notifications. So we only give a warning but allow them to toggle.
rename fcn notifications::send_notification -> notifications::send
Changelog update

Changelog update for pull request #240.
move notifications into desktop namespace, rename folder also

We also move the desktop_utils files to desktop/open.?pp, and
update the project files appropriately.
Fix the warn_early_init_failure message

The data dir path is set with --data-dir, not --config-dir. Somehow this
slipped past my internal radar despite reviewing the diff several times.
Merge pull request #250 from ancestral/master

Changelog update
check lobby_sounds preference for the GUI 1 lobby also

This fixes a bug reported on forums here:
http://forums.wesnoth.org/viewtopic.php?f=4&t=40660#p572131

The lobby sounds pref now affects the GUI 1 and 2 mp lobbies,
but it only affects the lobby screen, not mp::wait or mp::connect
etc.

This check is implemented by trying to dynamic cast 'this' mp::ui
object to a mp::lobby, at the time when we would play the arrive
or leave sounds.

The lobby sounds pref does *not* block the sounds due to server
messages, messages from a friend, or whispers.
update changelog
fixup error msg for when libdbus is not available
switch dbus log to log channel 'desktop'
fix a bug with the chat synposis generated by dbus notifications

When searching for the next line, if it didn't find one, index
npos would cause it to wrap around unexpectedly.
fixup notifications records data structure

Changed it from a list, which would be sequentially searched by id
and owner, to a multi_index container using hashed indices for both
of these fields.
fixup to dbus notifications: only chat msgs have history synopsis
fix wesnoth icon not appearing with dbus notifications
update changelogs
update players_changelog with note about the lobby_sounds fix