CMake: Changed slash format to support MSYS.
CMake: Changed slash format to support MSYS.

Ref.: #1044

Haxi52/cuberite,Haxi52/cuberite,nevercast/cuberite,kevinr/cuberite,electromatter/cuberite,Howaner/MCServer,mmdk95/cuberite,Haxi52/cuberite,nevercast/cuberite,bendl/cuberite,Fighter19/cuberite,Howaner/MCServer,Frownigami1/cuberite,jammet/MCServer,mjssw/cuberite,ionux/MCServer,electromatter/cuberite,marvinkopf/cuberite,kevinr/cuberite,SamOatesPlugins/cuberite,electromatter/cuberite,linnemannr/MCServer,thetaeo/cuberite,birkett/MCServer,nounoursheureux/MCServer,jammet/MCServer,nevercast/cuberite,birkett/MCServer,birkett/MCServer,birkett/cuberite,zackp30/cuberite,tonibm19/cuberite,Tri125/MCServer,Fighter19/cuberite,guijun/MCServer,ionux/MCServer,kevinr/cuberite,nichwall/cuberite,Schwertspize/cuberite,ionux/MCServer,guijun/MCServer,linnemannr/MCServer,Tri125/MCServer,SamOatesPlugins/cuberite,nicodinh/cuberite,Altenius/cuberite,QUSpilPrgm/cuberite,nevercast/cuberite,jammet/MCServer,birkett/cuberite,nounoursheureux/MCServer,marvinkopf/cuberite,thetaeo/cuberite,mjssw/cuberite,SamOatesPlugins/cuberite,Haxi52/cuberite,mjssw/cuberite,bendl/cuberite,birkett/MCServer,nicodinh/cuberite,mmdk95/cuberite,guijun/MCServer,johnsoch/cuberite,Haxi52/cuberite,thetaeo/cuberite,tonibm19/cuberite,ionux/MCServer,HelenaKitty/EbooMC,SamOatesPlugins/cuberite,QUSpilPrgm/cuberite,mmdk95/cuberite,Altenius/cuberite,Fighter19/cuberite,zackp30/cuberite,mc-server/MCServer,guijun/MCServer,nounoursheureux/MCServer,Frownigami1/cuberite,mjssw/cuberite,guijun/MCServer,linnemannr/MCServer,nichwall/cuberite,johnsoch/cuberite,Fighter19/cuberite,Tri125/MCServer,johnsoch/cuberite,tonibm19/cuberite,Frownigami1/cuberite,bendl/cuberite,Frownigami1/cuberite,Tri125/MCServer,marvinkopf/cuberite,zackp30/cuberite,mc-server/MCServer,tonibm19/cuberite,mc-server/MCServer,birkett/cuberite,mjssw/cuberite,nounoursheureux/MCServer,zackp30/cuberite,electromatter/cuberite,nevercast/cuberite,nichwall/cuberite,nevercast/cuberite,Fighter19/cuberite,nounoursheureux/MCServer,QUSpilPrgm/cuberite,nicodinh/cuberite,tonibm19/cuberite,nichwall/cuberite,mjssw/cuberite,kevinr/cuberite,linnemannr/MCServer,bendl/cuberite,birkett/MCServer,Howaner/MCServer,SamOatesPlugins/cuberite,kevinr/cuberite,mc-server/MCServer,Frownigami1/cuberite,nicodinh/cuberite,thetaeo/cuberite,mmdk95/cuberite,jammet/MCServer,Schwertspize/cuberite,Haxi52/cuberite,HelenaKitty/EbooMC,johnsoch/cuberite,QUSpilPrgm/cuberite,mmdk95/cuberite,Altenius/cuberite,Altenius/cuberite,QUSpilPrgm/cuberite,bendl/cuberite,zackp30/cuberite,jammet/MCServer,Schwertspize/cuberite,marvinkopf/cuberite,Schwertspize/cuberite,electromatter/cuberite,linnemannr/MCServer,mc-server/MCServer,johnsoch/cuberite,Howaner/MCServer,QUSpilPrgm/cuberite,marvinkopf/cuberite,Tri125/MCServer,Howaner/MCServer,Fighter19/cuberite,guijun/MCServer,Schwertspize/cuberite,thetaeo/cuberite,tonibm19/cuberite,birkett/cuberite,jammet/MCServer,birkett/MCServer,nicodinh/cuberite,ionux/MCServer,kevinr/cuberite,birkett/cuberite,thetaeo/cuberite,zackp30/cuberite,Altenius/cuberite,ionux/MCServer,electromatter/cuberite,mmdk95/cuberite,mc-server/MCServer,nicodinh/cuberite,HelenaKitty/EbooMC,nichwall/cuberite,Howaner/MCServer,HelenaKitty/EbooMC,birkett/cuberite,linnemannr/MCServer,nichwall/cuberite,marvinkopf/cuberite,nounoursheureux/MCServer,HelenaKitty/EbooMC,Tri125/MCServer