Add warning for a zip file entry 4 GiB or larger.

pigz currently will not generate a ZIP64 format .zip file if the
input uncompressed or compressed lengths are greater than or equal
to 4 GiB. This commit issues a warning in that instance that the
resulting .zip file will be unusable.

pigz.c

@@ -1048,6 +1048,8 @@ local void put_trailer(unsigned long ulen, unsigned long clen,
         PUT4L(tail + 8, clen);
         PUT4L(tail + 12, ulen);
         writen(g.outd, tail, 16);
+        if (clen > UINT32_MAX || ulen > UINT32_MAX)
+            complain("4 GiB or greater length: %s will be unusable", g.outf);
 
         /* write central file header */
         PUT4L(tail, 0x02014b50UL);  /* central header signature */