Stop using g_uri_escape_string() to escape the URI before launching it.

This was wrong. Take this URL as an example:
https://developer.pidgin.im/search?q=brains&noquickjump=1&wiki=on

When escaped with g_uri_escape_string() it becomes:
https://developer.pidgin.im/search%3Fq%3Dbrains%26noquickjump%3D1%26wiki%3Don

?, = and & are replaced with %3F, %3D and %26 which means they are considered part of the path component rather than query args. I tested and I get 404s when launching that URL with Firefox, Google Chrome, and these manual commands: gnome-open, xdg-open, firefox, google-chrome.

Strangely I DON'T get a 404 when I launch the URL with Konqueror. The original unescaped URL loads. I consider this to be a bug in Konqueror. They would fail to load when launched with a URL that has a question mark as part of the path component because they would convert the remaining path into the query string.

So I ripped out uri_escaped and used uri in its place everywhere.

This bug never got released. We changed the behavior because someone reported
to us that this URL:
http://example.org/$(xterm)
caused xterm to be executed on his system. Obviously that's bad if that
happens, but I don't think it's a bug in Pidgin. We're correctly escaping
all arguments that we pass to the browser command. If a system unescapes those
at some point and execs them, then that system is dangerously broken.

I tested this newest code with Firefox, Google Chrome, Konqueror, and the
manual commands gnome-open and xdg-open and they all work perfectly for me.