Adding missing include for ‘getcwd’ and ‘chdir’

#### Problem

	git clone git://github.com/jjgod/wiiscrubber-ng.git
	cd wiiscrubber-ng/
	mkdir -p bin; cd bin
	cmake ..
	colormake
	
	/home/user/repo/wiiscrubber-ng/src/WIIDisc.cpp:4215:31: error: ‘getcwd’ was not declared in this scope
	/home/user/repo/wiiscrubber-ng/src/WIIDisc.cpp:4221:21: error: ‘chdir’ was not declared in this scope