Fix CVE-2017-5974:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5974

Patch copied from Debian.

Index: zziplib-0.13.62/zzip/memdisk.c
===================================================================
--- zziplib-0.13.62.orig/zzip/memdisk.c
+++ zziplib-0.13.62/zzip/memdisk.c
@@ -216,12 +216,12 @@ zzip_mem_entry_new(ZZIP_DISK * disk, ZZI
         /* override sizes/offsets with zip64 values for largefile support */
         zzip_extra_zip64 *block = (zzip_extra_zip64 *)
             zzip_mem_entry_extra_block(item, ZZIP_EXTRA_zip64);
-        if (block)
+        if (block && ZZIP_GET16(block->z_datasize) >= (8 + 8 + 8 + 4))
         {
-            item->zz_usize = __zzip_get64(block->z_usize);
-            item->zz_csize = __zzip_get64(block->z_csize);
-            item->zz_offset = __zzip_get64(block->z_offset);
-            item->zz_diskstart = __zzip_get32(block->z_diskstart);
+            item->zz_usize = ZZIP_GET64(block->z_usize);
+            item->zz_csize = ZZIP_GET64(block->z_csize);
+            item->zz_offset = ZZIP_GET64(block->z_offset);
+            item->zz_diskstart = ZZIP_GET32(block->z_diskstart);
         }
     }
     /* NOTE:
uix/log/gnu/system/nss.scm'>log</a><a href='/guix/tree/gnu/system/nss.scm?id=efb895146097fa14a8a38fe6de127f01aaf2a37b'>tree</a><a href='/guix/commit/gnu/system/nss.scm?id=efb895146097fa14a8a38fe6de127f01aaf2a37b'>commit</a><a href='/guix/diff/gnu/system/nss.scm?id=efb895146097fa14a8a38fe6de127f01aaf2a37b'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/system/nss.scm'>
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<option value='grep'>log msg</option>
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<option value='range'>range</option>
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<div class='path'>path: <a href='/guix/log/?id=efb895146097fa14a8a38fe6de127f01aaf2a37b'>root</a>/<a href='/guix/log/gnu?id=efb895146097fa14a8a38fe6de127f01aaf2a37b'>gnu</a>/<a href='/guix/log/gnu/system?id=efb895146097fa14a8a38fe6de127f01aaf2a37b'>system</a>/<a href='/guix/log/gnu/system/nss.scm?id=efb895146097fa14a8a38fe6de127f01aaf2a37b'>nss.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/system/nss.scm?id=efb895146097fa14a8a38fe6de127f01aaf2a37b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-03-27 23:26:15 +0200'>2018-03-27</span></td><td><a href='/guix/commit/gnu/system/nss.scm?id=f7a5cf7a2da9590fe64e85e6f263b11020e943aa'>nss: Remove '%compat' from the defaults.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>