libziparchive: fix calculation of mod_time.

Take mod_date into account as well, and fixes the issue where
all entries had creation dates in 1979.

Signed-off-by: beonit <beonit@gmail.com>
Change-Id: Id101794fa08218d15f2d1ba4e4a313c1807ea7aa
diff --git a/libziparchive/zip_archive_test.cc b/libziparchive/zip_archive_test.cc
index 9a3cdb4..32b1a38 100644
--- a/libziparchive/zip_archive_test.cc
+++ b/libziparchive/zip_archive_test.cc
@@ -272,6 +272,7 @@
   ASSERT_EQ(static_cast<uint32_t>(17), data.uncompressed_length);
   ASSERT_EQ(static_cast<uint32_t>(13), data.compressed_length);
   ASSERT_EQ(0x950821c5, data.crc32);
+  ASSERT_EQ(static_cast<uint32_t>(0x438a8005), data.mod_time);
 
   // An entry that doesn't exist. Should be a negative return code.
   ZipString absent_name;