Security update for zsh (moderate)

This update for zsh to version 5.5 fixes the following issues:

Security issues fixed:

• CVE-2018-1100: Fixes a buffer overflow in utils.c:checkmailpath() that
  can lead to local arbitrary code execution (bsc#1089030)
• CVE-2018-1071: Fixed a stack-based buffer overflow in exec.c:hashcmd()
  (bsc#1084656)
• CVE-2018-1083: Fixed a stack-based buffer overflow in
  gen_matches_files() at compctl.c (bsc#1087026)

Non-security issues fixed:

• The effect of the NO_INTERACTIVE_COMMENTS option extends into $(…) and
  ... command substitutions when used on the command line.
• The ‘exec’ and ‘command’ precommand modifiers, and options to them, are
  now parsed after parameter expansion.
• Functions executed by ZLE widgets no longer have their standard input
  closed, but redirected from /dev/null instead.
• There is an option WARN_NESTED_VAR, a companion to the existing
  WARN_CREATE_GLOBAL that causes a warning if a function updates a
  variable from an enclosing scope without using typeset -g.
• zmodload now has an option -s to be silent on a failure to find a module
  but still print other errors.

This update was imported from the SUSE:SLE-15:Update update project.