Renamed glib packages

I'm going to normalize the package names in gi-rust, while also switching
to generated code that provides nearly all of the library API. This
package is one of the few that depends on the current name.

Cargo.toml

@@ -12,5 +12,5 @@ keywords = ["libnotify", "notification"]
 
 [dependencies]
 libnotify-sys = "*"
-glib-2_0-sys = "*"
+glib-2-0-sys = "*"
 gtypes = "*"