internal/system: relocate from system

These packages are highly specific to hakurei and are difficult to use safely from other pieces of code.

Their exported symbols are made available until v0.4.0 where they will be removed for #24.

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

internal/system/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)
+}