Enable `add_stylesheet` etc to generate links outside the `chrome` path: if they start with a slash, they're considered relative to the application root URL, otherwise the link gets prefixed with `chrome/`.
Enable `add_stylesheet` etc to generate links outside the `chrome` path: if they start with a slash, they're considered relative to the application root URL, otherwise the link gets prefixed with `chrome/`.

git-svn-id: f68c6b3b1dcd5d00a2560c384475aaef3bc99487@4346 af82e41b-90c4-0310-8c96-b1721e28e2e2

exocad/exotrac,moreati/trac-gitsvn,moreati/trac-gitsvn,dokipen/trac,moreati/trac-gitsvn,dafrito/trac-mirror,exocad/exotrac,dafrito/trac-mirror,moreati/trac-gitsvn,dokipen/trac,dafrito/trac-mirror,dokipen/trac,exocad/exotrac,exocad/exotrac,dafrito/trac-mirror