add "write_to" parameter to wml_message

"write_to" lets the wmldev specify to where the message should be
written. Defaults to the previous behaviour.

The intention is for example that one might want to give a summary  as a
chat message and a very detailed information in the stderr file.
replace write_to with to_chat in [wml_message]

as shadowm suggested, because we are never in the situation that we want
this information in the chat but not in the stderr.
add static const members ZERO, default_dirs, of map_location

Replace local constants appearing elsewhere with these.
The definitions are inlined.
inline the definition map_location::null_location

If we decided it was worth it to inline map_location ==, then
surely this is also worth it to inline null_location, as the
compiler may be able to reduce tests for == null location to
"x == ... && y == ...", without having to move to a different
compilation unit.
fixup travis (failure to find preferences is not reported as error)
enable full debugging the first time travis runs scripts

Revert this once the tests start passing
refactor strict logging

Don't throw an exception, just remember that we broke strict mode,
and cause the unit test to fail if that happens.
Merge pull request #166 from gfgtdf/wml_message

add "to_chat" parameter to wml_message
#include <map.hpp> -> #include "map.hpp"
always flush filesystem errors (so we can see on travis)
Merge branch 'master' of git://github.com/wesnoth/wesnoth
Make sure all error logs flush with std::endl, so we get on travis.

This is the result of running this command in directory src/

find . -type f -exec sed -i 's/\(ERR.*\)\\n\"\;/\1\" << std::endl\;/g' '{}' \;

and carefully inspecting the results.
Make sure all warning logs are flushed, so travis gets the results.

This is the result of running command, in src/,

find . -type f -exec sed -i 's/\(WRN.*\)\\n\"\;/\1\" << std::endl\;/g' '{}' \;

and inspecting the results.

Also ran this subsequently:

find . -type f -exec sed -i 's/\(WARN.*\)\\n\"\;/\1\" << std::endl\;/g' '{}' \;

which only affected render.cpp
cleanup previous two find and replace results

Just wanted to remove the empty strings that got created:

find . -type f -exec sed -i 's/<< "" <</<</g' '{}' \;

find . -type f -exec sed -i 's/<<"" <</<</g' '{}' \;

I also unstaged tools/schema/tags.cpp, since I don't think I changed
that.
travis requires all unit tests to pass. also refactor run_wml_tests.

With the change to --log-strict, it's not necessary to rerun with
strict mode off, so we can get rid of part of the old system.

Feel free to revert this is you don't want travis to require all
unit tests to pass as part of the build.
clean up map_locations.hpp, put inline bodies at end

Also, move vector ops to inline as well.
inline get_adjacent, tiles_adjacent, distance_between (map_locations)
refactor tiles_adjacent, use jump tables instead of math abs
wmllint GUI: used a smaller icon for the Browse button, and made the entry fill the whole frame
wmllint GUI: made two labelframe labels shorter