gecko-embed API additions

[Owen Williams]

I develop an RSS reader called PenguinTV[1] that I am adapting for use
on the olpc.  Right now I use gtkhtml for my program, but I'd like to
adapt it for gecko-embed.  However there are some gaps in the API that
makes it impossible to use in its current state.

Right now there is no way to tell the widget to load arbitrary html
data.  I need to do this to render my RSS pages, and I can imagine that
other projects would also want to be able to display arbitrary html.  In
gtkmozembed, there are three functions that provide this functionality:
open_stream, append_data, and close_stream.  I think it would be
reasonable to add these functions to the python API.

The other thing I need is to be able to tell moz that I don't want it to
respond to links clicked in the browser.  For instance, my application
handles all of the URIs itself, and performs actions for some internal
pseudo-URIs or spawns a new browser window (activity) for any external
internet links that are clicked.

Currently, gtkmozembed enables this behavior by listening to the
response to the "open-uri" signal.  If I return True from my handler,
moz cancels the page load.  While this seems acceptable to me, I was
chatting with Marco and he said there were problems with this scheme.
The specific mechanism doesn't make a big difference to me, but I need
to be able to prevent gecko-embed from loading new pages unless I tell
it to.  

I think these changes are reasonable, considering that they allow
gecko-embed to be used anywhere one wants html renderring but not web
browsing.  It could apply to email, rss, or chat.

Thanks,
Owen Williams

[1]http://penguintv.sourceforge.net