Add a pairing agent for Remote

Remote is the iPod/iPhone application that can act as a remote control for
iTunes. Remote must be paired with an iTunes instance before it can control
it; this pairing process includes a challenge/response autentication.

This pairing agent makes it possible to pair Remote with a forked-daapd
instance. It is the very first step for Remote support.

src/remote_pairing.h

@@ -0,0 +1,14 @@
+
+#ifndef __REMOTE_PAIRING_H__
+#define __REMOTE_PAIRING_H__
+
+void
+remote_pairing_read_pin(char *path);
+
+int
+remote_pairing_init(void);
+
+void
+remote_pairing_deinit(void);
+
+#endif /* !__REMOTE_PAIRING_H__ */