fixup pandora compilation with SDL < 1.2.12

This was checked to compile (but not link of course) on my system,
using cmake with pandora enabled, and pointed to the SDL_mixer
1.2.0 header.
Merge branch 'master' of https://github.com/wesnoth/wesnoth
Merge branch 'master' of https://github.com/wesnoth/wesnoth
Restore string constness intention lost in Boost.locale deployment

These few strings were used as though `const char* const` was intended
but their indirect value constness was dropped during the conversion
since their pointer value was not const.
remove an unnecessary ppa from travis

Because we are including saucy now (to get SDL mixer 1.2.12),
adding this test ppa is unnecessary (saucy has g++-4.8), and it
can only serve to confuse / cause us to accidentally get
mismatching lib versions, so I remove it
Merge branch 'master' of https://github.com/wesnoth/wesnoth
resolve ambiguities in referring to std::abs, in map_location.hpp

Ancestral reported compilation errors with clang on OS X,
basically similar to what is reported here:

https://github.com/Project-OSRM/osrm-backend/issues/1000

I fix it by replacing calls to std::abs, with calls to _abs, a
function pointer I define to be & _abs, so that I can control
exactly which overload is selected and thus resolve the ambiguity.
fixup compilation for OS X

Apparently OS X does not provide an int std::abs(int) at all, or
we aren't including it properly or someting. I work around this.
Xcode project: finish switching to using the new boost filesystem code

This includes adding a new library (libboost_localew.dylib; with
libboost_filesystemw.dylib already having been added a few days ago),
so a new version of the Mac compile package is needed for compiling.
Release notes: Add comment about new Xcode compile package requirement
Changelog: Add comment about new Xcode compile package requirement
fixup std::abs in map_location.hpp

The reason that OS X wasn't finding std::abs(int) is that we
weren't including <cstdlib>, which is where it resides, not
<cmath>. This commit adds cstdlib, and reverts the other fix
attempts.

This fixes up two previous commits:

b05773c4099e9a2c987adc0c656ec7ed96dec0ff

7ce9199e470025b69935812d8445fc280767fb42
scons: add selected headers for boost libs locale, random
fixup b88d2af26fbac5157f4c084bc08ce250a5c66c58
Spanish translation update
fix "time over" event in replays
fix start-of-scenario 1.13 compability (#22546)