contrib/tcsh_completion

run-tests: include quotes in the HGEDITOR value when storing sys.executable

This fixes test-install.t on Windows that broke in 2122b82b6987 when
shlex.split() was added to the debuginstall command:

    @@ -7,8 +7,11 @@
       checking installed modules (*mercurial)... (glob)
       checking templates (*mercurial?templates)... (glob)
       checking commit editor...
    +   Can't find editor 'c:\Python27\python.exe -c "(omitted)"' in PATH
    +   (specify a commit editor in your configuration file)
       checking username...
    -  no problems detected
    +  1 problems detected, please check your install!
    +  [1]

What happens is that shlex.split() on Windows turns this:

    c:\Python27\python.exe -c "import sys; sys.exit(0)"

into this:

    ['c:Python27python.exe', '-c', 'import sys; sys.exit(0)']

While technically a regression, most programs on Windows live in some flavor of
'Program Files', and therefore the environment variable needs to contain quotes
anyway to handle the space.  This wasn't handled prior to the shlex() change,
because it tested the whole environment variable to see if it was an executable,
or split on the first space and tested again.

#
# tcsh completion for Mercurial
#
# This file has been auto-generated by tcsh_completion_build.sh for
# Mercurial Distributed SCM (version 1.7.5+157-8a220ae0b2ba)
#
# Copyright (C) 2005 TK Soh.
#
# This is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 2 of the License, or (at your
# option) any later version.
#

complete hg \
  'n/--cwd/d/' 'n/-R/d/' 'n/--repository/d/' \
  'C/-/( -R --repository \
    --cwd \
    -y --noninteractive \
    -q --quiet \
    -v --verbose \
    --config \
    --debug \
    --debugger \
    --encoding \
    --encodingmode \
    --traceback \
    --time \
    --profile \
    --version \
    -h --help)/' \
  'p/1/(add addremove annotate blame archive \
    backout bisect bookmarks branch branches \
    bundle cat clone commit ci \
    copy cp debugancestor debugbuilddag debugcheckstate \
    debugcommands debugcomplete debugdag debugdata debugdate \
    debugfsinfo debugignore debugindex debugindexdot debuginstall \
    debugpushkey debugrebuildstate debugrename debugrevspec debugsetparents \
    debugstate debugsub debugwalk diff export \
    forget grep heads help identify \
    id import patch incoming in \
    init locate log history manifest \
    merge outgoing out parents paths \
    pull push recover remove rm \
    rename move mv resolve revert \
    rollback root serve showconfig debugconfig \
    status st summary sum tag \
    tags tip unbundle update up \
    checkout co verify version)/'