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

util-linux/more.c

@@ -29,6 +29,7 @@
 #include <stdio.h>
 #include <fcntl.h>
 #include <signal.h>
+#include <stdlib.h>
 #include <sys/ioctl.h>
 #define BB_DECLARE_EXTERN
 #define bb_need_help