copyright_holder and comment_tag options fail on Windows

[ccprog]

These two options require quoting; Windows only knows about double quotes for that.

The task consequently fails with "unable to find file" returned from xgettext

[stephenharris]

Sorry, this is months old but, do you mean to say that on Windows the copyright-holder option would be the following

 --copyright-holder="{value}"

using singled quotes, as opposed to

 --copyright-holder='{value}'

[ccprog]

On Windows, only "{value}" quotes are known. See http://ss64.com/nt/syntax-esc.html. '{value}' is only defined in Unix/Linux shells.