tools/nolibc: add stdint.h

Nolibc works fine for small and limited program however most program
expect integer types to be defined in stdint.h rather than std.h.

This is a quick fix that moves the existing integer definitions in std.h
to stdint.h.

Signed-off-by: Vincent Dagonneau <v@vda.io>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>