debuginstall: strip double quotes from editorbin on Windows
The unconditional posix style shlex.split() prior to
94a1ff16f362 handled this.
This isn't mutually exclusive with stripping the quotes in util.findexe()- if
the editor can't be found, this command prints out the string, inside single
quotes.
#require docutils gettext
$ $TESTDIR/check-gendoc da
checking for parse errors