Append bytes to an array
#include <array.h>
void array_catb(array* x,const char* y,int64 len);
array x; const char* y; int64 len; array_catb(&x,y,len);
array_catb appends the bytes y[0], y[1], ..., y[len-1] to the array x. It handles failure in the same way as array_cat.