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

coreutils/ls.c

@@ -59,6 +59,7 @@ static const int COLUMN_GAP = 2;			/* includes the file type char, if present */
 #include <time.h>
 #endif
 #include <string.h>
+#include <stdlib.h>
 
 #include <fcntl.h>
 #include <signal.h>