Updated big button graphics by LordBob

From <http://r.wesnoth.org/p577072>.

Fixes a weird light source angle issue with the active variants.
dont always show mpconnect in debugmode in sp
reorder gettext.hpp
make gettext.hpp return std::string s.
use boost locale gettext
fix unused warnings.
fix compilation

it seems like sometimes libintl.h is needed for LC_MESSAGES so we need
to move that last code that uses LV_MESSAGES out of language.cpp into
gettext.cpp
fix comilation

move LC_MESSAGES out of wesnoth.cpp and game_config_manager.cpp
fix gettext_boost.cpp
add include
fix image translations