Kernel/LibC: add mmap for private anonymous mappings

This will be used by the userspace to get more memory. Currently
kernel handles all allocations, which is not preferable.

libc/CMakeLists.txt

@@ -13,6 +13,7 @@ set(LIBC_SOURCES
 	stdio.cpp
 	stdlib.cpp
 	string.cpp
+	sys/mman.cpp
 	sys/stat.cpp
 	sys/wait.cpp
 	termios.cpp