Fix undefined behaviour. * lib/bitrotate.h (rotl16, rotr16, rotl8, rotr8): Case x to 'unsigned int', to avoid shift operations on 'int'. * lib/xmemdup0.c (xmemdup0): Don't invoke memcpy with a zero size. * tests/test-count-leading-zeros.c (main): Use a random number that has as many bits as TYPE, not only 2*15 or 2*31 bits. * tests/test-count-trailing-zeros.c (main): Likewise. * tests/test-count-one-bits.c (main): Likewise. * tests/test-memmem.c: Don't include "null-ptr.h". (main): Use zerosize_ptr() instead of null_ptr(). * modules/memmem-tests (Files): Remove tests/null-ptr.h.