signextend
read_leb128(struct dwbuf *d, uint64_t *v, bool signextend)
if (signextend && shift < 64 && (x & 0x40) != 0)
long signextend(unsigned long, int);
M = signextend((((short)(s1->m_tolerance & 0xC0)) << 2) + s1->m, 10);
B = signextend((((short)(s1->b_accuracy & 0xC0)) << 2) + s1->b, 10);
K1 = signextend(s1->rbexp & 0xF, 4);
K2 = signextend(s1->rbexp >> 4, 4);
if (signextend && shift < 64 && (x & 0x40) != 0)
dw_read_leb128(struct dwbuf *d, uint64_t *v, int signextend)