Work around a bug in macOS Archiver.

It uses data descriptors, but sets the compressed size (and only
that) in the local header (contrary to what appnote.txt says).

Accept this if it matches the value in the central directory.

Closes #341

lib/zip_open.c

@@ -491,9 +491,20 @@ _zip_headercomp(const zip_dirent_t *central, const zip_dirent_t *local) {
 
     if ((central->crc != local->crc) || (central->comp_size != local->comp_size) || (central->uncomp_size != local->uncomp_size)) {
         /* InfoZip stores valid values in local header even when data descriptor is used.
-           This is in violation of the appnote. */
-        if (((local->bitflags & ZIP_GPBF_DATA_DESCRIPTOR) == 0 || local->crc != 0 || local->comp_size != 0 || local->uncomp_size != 0))
+           This is in violation of the appnote.
+	   macOS Archive sets the compressed size even when data descriptor is used ( but not the others),
+	   also in violation of the appnote.
+	*/
+	/* if data descriptor is not used, the values must match */
+        if ((local->bitflags & ZIP_GPBF_DATA_DESCRIPTOR) == 0) {
             return -1;
+	}
+	/* when using a data descriptor, the local header value must be zero or match */
+	if ((local->crc != 0 && central->crc != local->crc) ||
+	    (local->comp_size != 0 && central->comp_size != local->comp_size) ||
+	    (local->uncomp_size != 0 && central->uncomp_size != local->uncomp_size)) {
+	    return -1;
+	}
     }
 
     return 0;