do not include <sys/stat.h> just before "libbb.h", it's there already

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/isdirectory.c b/libbb/isdirectory.c
index 462aa00..6225a34 100644
--- a/libbb/isdirectory.c
+++ b/libbb/isdirectory.c
@@ -7,7 +7,6 @@
  *
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
-#include <sys/stat.h>
 #include "libbb.h"
 
 /*
diff --git a/libbb/mode_string.c b/libbb/mode_string.c
index 280e6d2..5ffd568 100644
--- a/libbb/mode_string.c
+++ b/libbb/mode_string.c
@@ -6,13 +6,7 @@
  *
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
-
-/* Aug 13, 2003
- * Fix a bug reported by junkio@cox.net involving the mode_chars index.
- */
 #include <assert.h>
-#include <sys/stat.h>
-
 #include "libbb.h"
 
 #if ( S_ISUID != 04000 ) || ( S_ISGID != 02000 ) || ( S_ISVTX != 01000 ) \