change length or size specifiers in APIs from int to long

add array API (http://cr.yp.to/lib/array.html)

array/array_equal.c

@@ -0,0 +1,7 @@
+#include "byte.h"
+#include "array.h"
+
+int array_equal(const array* const x,const array* const y) {
+  if (x->initialized!=y->initialized) return 0;
+  return byte_equal(x->p,x->initialized,y->p);
+}