Log Message:
links{,-gui}: Update to 2.20

Changes:
2.20
----
 - Security bug fixed: when links was connected to tor, it would send real
   dns requests outside the tor network when the displayed page contains
   <link rel="dns-prefetch" href="http://host.domain/">.
   This bug is present in links-2.15 to links-2.19.
   Found by Shi Tian.
 - Fix a crash if:
    * External fonts are used
    * Rendering is optimized for LCD
    * The document contains some characters with zero width
 - Accept file urls in the form file://localhost/usr/bin/ or
   file://hostname/usr/bin/ according to RFC 8089
 - Report errors using dialog boxes on OS/2 and Windows because
   the standard output may not be visible
 - Fix an error "ERROR: select for write (5) failed: Bad file descriptor"
   that could happen if the master process was doing dns lookup while being
   suspended
 - Fixed a memory leak of the SSL structure
 - Try to open the file "/dev/input/mice" and use it instead of gpm.
   (the user must be in the "input" group)
   This results in smooth mouse movement on the framebuffer.
 - Report "Lynx/Links" user agent when searching on Google so that
   Google returns non-css page
 - Support the zstd compression algorithm
 - Haiku support
 - Fix mouse dragging not being reported in xterm
 - Use proper cookie expiry