xBRZ trial commit

This commit adds the xBRZ algorithm to the codebase, and hacks in
an imagepath modification to use it, and adds a bunch of extra
images showcasing it to the unit help pages.

xBRZ was obtained from sourceforge (xBRZ.zip):
http://sourceforge.net/projects/hqmame/files/

It is modified, the original program wants to be compiled as
C++11, so I had to make minor changes so that it can compile as
C++98 w/ boost.

Main changes: get boost/cstdint and typedef uint32_t from there,
comment out all static asserts
change all cases of lambda functions to boost bind instances or
otherwise.
Fix non-utf8 characters.
Suppress warnings from unused functions.

dos2unix on all new files
fixup xbrz blending handling of alpha channel
add wesnoth default scaling results along-side xBRZ in help pages
Revert "Anchor unit overlays to the topleft corner of the sprite."

This reverts commit 8f49cbad5508d761c1139c65e064c31ea3c79a00.

This commit breaks the game when you zoom in, since I'm trying to
make changes to how that works it is inconvenient to have to deal
with it right now. This bug was assigned to lipk more than a month
ago when he first introduced it.

Conflicts:
	changelog
	src/unit_drawer.cpp
as a test, use xBRZ when zooming images

This also sets the max zoom to 288 so you can reach 3x and 4x if
desired.