smooth unit movement over terrain with elevation
fixup project files after rename builder.?pp -> terrain_builder.?pp

This fixes up earlier commit 8fafdbecd42d
Merge branch 'master' of git://github.com/wesnoth/wesnoth
don't move health bar with unit where terrain elvation differs.
visualize relative dir routine
add sanity check for vector_negation, based on random walk.
add sanity check for get_direction

check that it corresponds to adding vectors of length one
Fix implementation of map_location::get_relative_dir
Fix code comment with last commit
update characterization test for get_relative_dir
Merge branch 'test_relative_dir'
disable the get_relative_dir visualizer
Merge branch 'master' of git://github.com/wesnoth/wesnoth
Update Xcode project
Move legacy map_location arithmetic to terrain_builder.cpp

This is the only place where it is now used, so we move it out
of the map_location.?pp files and into the private space of
terrain_builder.cpp
Merge branch 'master' of git://github.com/wesnoth/wesnoth
Only blit neutral surfaces.

On the Mac loaded images are not in the neutral format causing rendering
glitches when using blit_surface using these images. Test and when
needed convert the image before using it.

Fixes bug #22045.
add setter for team.fight_on_without_leader

to be able to set this value from lua.
expose side.lost and fight_on_without_leader to lua
add 3-way tests for map_location, like associativity. refactor.

Tried also to assert translation invariance of get_relative_dir,
but that doesn't seem to hold atm.