Type cleanup, internally and in the API.  Fixes most llvm warnings.
diff --git a/lib/zip_discard.c b/lib/zip_discard.c
index 29aa25e..37ba8c2 100644
--- a/lib/zip_discard.c
+++ b/lib/zip_discard.c
@@ -46,7 +46,7 @@
 void
 zip_discard(struct zip *za)
 {
-    int i;
+    zip_uint64_t i;
 
     if (za == NULL)
 	return;