Remove unneeded header files from source files throughout.

winsup/cygwin/dir.cc

@@ -9,14 +9,11 @@ Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
 details. */
 
 #include "winsup.h"
-#include <unistd.h>
 #include <stdlib.h>
-#include <sys/stat.h>
 
 #define _COMPILING_NEWLIB
 #include <dirent.h>
 
-#include "pinfo.h"
 #include "cygerrno.h"
 #include "security.h"
 #include "path.h"
@@ -24,8 +21,6 @@ details. */
 #include "dtable.h"
 #include "cygheap.h"
 #include "cygtls.h"
-#include "perprocess.h"
-#include "cygwin/version.h"
 
 extern "C" int
 dirfd (DIR *dir)