Fixed FindSFML.cmake not updating library entries when the user changes the value of SFML_STATIC_LIBRARIES after the initial configure (#637).
Re-enabled RPATH feature.

RPATH is especially useful when running debug builds for testing on *nix
operating systems, because the binaries (e.g. examples) include library
runtime path information. This allows you to skip installing SFML to the
system or adjusting PATH variables/ld config.
Fixed memory leak in Unix JoystickImpl, refactored joystick code for all platforms, prevent accelerometers registering as joysticks on Unix.
Amended based on comments from last commit.
Added support for OS X 10.10

Note: this only fix the compilation process. SFML was not thoroughly
tested on this OS yet.
Merge branch 'bugfix/joystick'
Updated OS X Pool Wrapper