Fix header file usage -- there were many unnecessary header files included in
busybox.h which slowed compiles.  I left only what was needed and then fixed up
all the apps to include their own header files.  I also fixed naming for pwd.h
and grp.h functions.  Tested to compile and run with libc5, glibc, and uClibc.
 -Erik
diff --git a/cat.c b/cat.c
index 151ce4e..a1b8782 100644
--- a/cat.c
+++ b/cat.c
@@ -22,7 +22,7 @@
  */
 
 #include "busybox.h"
-#include <stdio.h>
+#include <stdlib.h>
 
 extern int cat_main(int argc, char **argv)
 {