Kernel/LibC: Implement basic epoll

This implementation is on top of inodes instead of fds as linux does it.
If I start finding ports/software that relies on epoll allowing
duplicate inodes, I will do what linux does.

I'm probably missing multiple epoll_notify's which may cause hangs but
the system seems to work fine :dd:

kernel/CMakeLists.txt

@@ -17,6 +17,7 @@ set(KERNEL_SOURCES
 	kernel/Device/RandomDevice.cpp
 	kernel/Device/ZeroDevice.cpp
 	kernel/ELF.cpp
+	kernel/Epoll.cpp
 	kernel/Errors.cpp
 	kernel/FS/DevFS/FileSystem.cpp
 	kernel/FS/Ext2/FileSystem.cpp