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