dvdbreakpoints
dvdbreakpoints: Use unsigned integer constants in some places.

Fixes these warnings from GCC:
dvdbreakpoints.c: In function ‘main’:
dvdbreakpoints.c:419:25: warning: conversion to ‘uint’ from ‘int’ may change the sign of the result [-Wsign-conversion]
dvdbreakpoints.c:427:31: warning: conversion to ‘uint’ from ‘int’ may change the sign of the result [-Wsign-conversion]
dvdbreakpoints.c:428:29: warning: conversion to ‘uint’ from ‘int’ may change the sign of the result [-Wsign-conversion]
dvdbreakpoints.c:477:27: warning: conversion to ‘uint’ from ‘int’ may change the sign of the result [-Wsign-conversion]
dvdbreakpoints.c:478:31: warning: conversion to ‘uint’ from ‘int’ may change the sign of the result [-Wsign-conversion]
dvdbreakpoints.c:479:29: warning: conversion to ‘uint’ from ‘int’ may change the sign of the result [-Wsign-conversion]
bitreader: Add explicit cast for b->bits.

Fixes this warning from GCC:
bitreader.c: In function ‘read_bits’:
bitreader.c:41:41: warning: conversion to ‘uint’ from ‘u64’ may alter its value [-Wconversion]
Add layers: a tool to print a dvd_physical struct.