fix mp campaign modifications

the dependency manager cannot handle campaigns, we work around this by
forcing the dependency manager to accept any modifications for
campaigns.

fixes https://gna.org/bugs/index.php?22334
Work around clang defining __GNUC__
Merge branch 'master' of github.com:wesnoth/wesnoth
Improve dynamic cast null-check

Found by coverity
added Portuguese manual images
fixed typo in CMakeLists sources list
add a design note to src/help/help_impl.?pp
fix quit during ai turn

fixes up https://github.com/wesnoth/wesnoth/commit/a65752a67696290c6f8a0e96c1b38c37c71535f5
add command history and history expansion to lua console

Adds an optional dependency on the readline library.
add "ilua" helper functions for lua interpreter
Station Guardian MAI: bug fix for unreachable stations

Keep guardian in place if the station is unreachable.
Merge branch 'master' of https://github.com/wesnoth/wesnoth
allow lua console to handle expressions

Implemented using ilua, and "experimental compilation" technique.
update changelog
scons, cmake: by default, search for GNU readline support
update_server: Show locations of scons' output
update_server: boost_prefix=-mt isn't good for gonzo anymore
refactor lua interpreter: clean up readline uses
refactor lua interpreter: move readline uses (history expansion)
add support for pageup / pagedown in lua_interpreter input bar