Fixes DLL linkage issues on Windows due to library rename, using different defines when projects are generated by CMake
Merge branch 'master' of https://github.com/libRocket/libRocket

# By Lee Zhen Yong
# Via David Wimsey (1) and Lee Zhen Yong (1)
* 'master' of https://github.com/libRocket/libRocket:
  bug fix: SFML2 example runtime error when application closes, caused by memory leaks