#6 Improve sniffing, detect Opera

[joao eiras]

Hi, sarissa could improve it's sniffing for browsers.
Currently all browser that support
document.implementation.createDocument are treated as
Mozilla. But this can't be removed otherwise many
application will fail to work with those other
browser, like Opera.

But sniffing for IE can be improved, and Opera still
isn't detected by Sarissa.

I've attached a patch file with my sugestion.

[joao eiras]

Patch with suggested changes to the sniffing