change length or size specifiers in APIs from int to long

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

array/array_catb.c

@@ -0,0 +1,16 @@
+#include "array.h"
+#include "byte.h"
+
+void array_catb(array* to,const char* from,uint64 len) {
+  long l;
+  if (to->allocated<0) return;
+  if (to->initialized+len<to->initialized) {
+fail:
+    array_fail(to);
+    return;
+  }
+  l=to->initialized;
+  if (!array_allocate(to,1,to->initialized+len))
+    goto fail;
+  byte_copy(to->p+l,to->initialized-l,from);
+}