system/internal/xcb: refactor and clean up

This package still does not deserve to be out of internal, but at least it is less haunting now. I am still not handling the xcb error though, the struct is almost entirely undocumented and the implementation is unreadable. Not even going to try.

Signed-off-by: Ophestra <cat@gensokyo.uk>

system/internal/xcb/changehosts.go

@@ -0,0 +1,17 @@
+package xcb
+
+import "errors"
+
+var ErrChangeHosts = errors.New("xcb_change_hosts() failed")
+
+func ChangeHosts(mode HostMode, family Family, address string) error {
+	conn := new(connection)
+	if err := conn.connect(); err != nil {
+		conn.disconnect()
+		return err
+	} else {
+		defer conn.disconnect()
+	}
+
+	return conn.changeHostsChecked(mode, family, address)
+}