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

dutmp.c

@@ -21,6 +21,8 @@
 #define bb_need_io_error
 #include "messages.c"
 #include <utmp.h>
+#include <stdlib.h>
+#include <unistd.h>
 
 extern int dutmp_main(int argc, char **argv)
 {
@@ -35,7 +37,7 @@ extern int dutmp_main(int argc, char **argv)
 	} else  {
 		file = open(argv[1], O_RDONLY);
 		if (file < 0) {
-			error_msg_and_die(io_error, argv[1], strerror(errno));
+			perror_msg_and_die(io_error, argv[1]);
 		}
 	}