Eliminate includes file and include locally as required.

File.cpp

@@ -1,5 +1,10 @@
 #include "File.h"
 #include "Exception.h"
+#include <sys/stat.h>
+#include <sstream>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 namespace coreutils {