Fix compilation.
Balancing tweaks

Limited number of bats Khrakrahs may have at a time, moved the dwarves
closer to the map edge where possible, and gave the Berserkers
predefined traits to prevent them from being quick (except one on hard).
Made the undead spawns require Jevyan to be alive
reword a line from the help about mixed terrains
Merge branch 'master' of git://github.com/wesnoth/wesnoth
Initial SDL_gpu support for dialogs.
SDL_Color-parametered overload for ttext::set_foreground_color.
Only redraw invalidated parts of the panel.

Fixes flickering buttons.
Fix compilation.
Add function draw_text_to_texture.
SDL_gpu implementation for the unit preview pane.
Don't share attributes among different sdl::timage instances.
Print FPS numbers to cerr in SDL_gpu builds.
Draw terrain overlays on the minimap.
Fix compilation.
Fix dialog borders.
fix copy assignment operator for unit class to work with refcount

This issue was spotted by gfgtdf. It doesn't appear that we
actually use this function -- prior to this commit, I tested a
version which had "assert(false)" at the start of this function,
and it was never triggered in normal play. But it's possible that
some lua command or obscure WML tag does use it.

It might also be a good idea to make the unit class noncopyable.
Merge branch 'master' of git://github.com/wesnoth/wesnoth
set travis to use gcc 4.6 again
Fix compilation with GCC 4.4.