add_script & add_stylesheet don't support external scripts

[martin@…]

Not sure if this was indented as a security feature, but:

The add_script from trac.web.chrome doesn't support external script URLs, i.e. one which start with 'http://'. At the moment the full URL is appended to the chrome path resulting in a dysfunctional script tag.

The same should be true for add_stylesheet.

If this is indented as a security feature, then be warned that it is easily overcome by just coping and changing the add_script source code, like I did in my GoogleMapMacro, where I have to load the external Google Map API JavaScript file.