extern const unsigned char sane_ctype[256];
#define GIT_DIGIT 0x02
#define isdigit(x) sane_istest(x,GIT_DIGIT)
#define sane_istest(x,mask) \
 ((sane_ctype[(unsigned char)(x)] & (mask)) != 0)
int versioncmp(....)
{
 int state;
 unsigned char c1;
 ....
 state = S_N + ((c1 == '0') + (isdigit(c1) != 0));
 ....
}