Added geo and gl packages from gogeline and improved documentation.

gl/drop.go

@@ -0,0 +1,15 @@
+package gl
+
+// The dropable interface is used to clean up GL objects.
+// Use the Drop() function to drop a range of objects.
+type Dropable interface {
+	Drop()
+}
+
+// Drops given GL objects.
+// Objects must implement the Dropable inteface.
+func Drop(objects []Dropable) {
+	for _, obj := range objects {
+		obj.Drop()
+	}
+}