Updated the alert() primitive to have a timeout.

  The timeout defaults to 60 seconds, and can be changed
 by the user:

   alert( "foo" )  -> Show the message "foo" until 60 seconds have
                      elapsed, or the user presses RET.

   alert( "bar", 5 ); -> Similar, but cancel after five seconds.
  Alert if we fail to parse a date: header.

  This fixes #77.
  Add a help-member to our array of Lua-callable primitives.

  This is not yet used, but it is easy to imagine:

      msg( help( "alert" ) );

  Or similar.
  Added more help-strings.
  Sync mail via offlineimap if available.

  This just moved the older code into a new function.
  Limit folders to google.com matches.
  Fixed comment to refer to get_signature.

  No the previous on_signature.
  Call on_signature for message replies too.

  Previously we only inserted the .sig for composed mails,
 and script-sent mails.
  Bound the access to the maildirs.

  This updates #69, and hopefully prevents the crash on resize.
  comment-update for the alert() function.
  Fix the signed vs. unsigned comparison
fix for #82 (index mode sdfsdf crash)
fix for #82 (index mode sdfsdf crash)
Merge branch 'master' of https://github.com/skx/lumail (#64)
  FIxup the colour-usage for body-drawing.
  GOTO considered harmful.

  I've replaced with a break.