[raop] Add support for Apple TV device verification, required by tvOS 10.2 (fix for issue #377)

- also change how speakers are saved/retrieved from the db
- add generic authorization methods in outputs.c and player.c
- let filescanner read *.verification files (containing PIN)
- configure options to enable and disable, since libsodium is required

src/outputs/raop_verification.h

@@ -0,0 +1,66 @@
+#ifndef __VERIFICATION_H__
+#define __VERIFICATION_H__
+
+#include <stdint.h>
+
+struct verification_setup_context;
+struct verification_verify_context;
+
+/* When you have the pin-code (must be 4 bytes), create a new context with this
+ * function and then call verification_setup_request1()
+ */
+struct verification_setup_context *
+verification_setup_new(const char *pin);
+void
+verification_setup_free(struct verification_setup_context *sctx);
+
+/* Returns last error message
+ */
+const char *
+verification_setup_errmsg(struct verification_setup_context *sctx);
+
+uint8_t *
+verification_setup_request1(uint32_t *len, struct verification_setup_context *sctx);
+uint8_t *
+verification_setup_request2(uint32_t *len, struct verification_setup_context *sctx);
+uint8_t *
+verification_setup_request3(uint32_t *len, struct verification_setup_context *sctx);
+
+int
+verification_setup_response1(struct verification_setup_context *sctx, const uint8_t *data, uint32_t data_len);
+int
+verification_setup_response2(struct verification_setup_context *sctx, const uint8_t *data, uint32_t data_len);
+int
+verification_setup_response3(struct verification_setup_context *sctx, const uint8_t *data, uint32_t data_len);
+
+/* Returns a 0-terminated string that is the authorisation key. The caller
+ * should save it and use it later to initialize verification_verify_new().
+ * Note that the pointer becomes invalid when you free sctx.
+ */
+int
+verification_setup_result(const char **authorisation_key, struct verification_setup_context *sctx);
+
+
+/* When you have completed the setup you can extract a key with
+ * verification_setup_result(). Give the string as input to this function to
+ * create a verification context and then call verification_verify_request1()
+ */
+struct verification_verify_context *
+verification_verify_new(const char *authorisation_key);
+void
+verification_verify_free(struct verification_verify_context *vctx);
+
+/* Returns last error message
+ */
+const char *
+verification_verify_errmsg(struct verification_verify_context *vctx);
+
+uint8_t *
+verification_verify_request1(uint32_t *len, struct verification_verify_context *vctx);
+uint8_t *
+verification_verify_request2(uint32_t *len, struct verification_verify_context *vctx);
+
+int
+verification_verify_response1(struct verification_verify_context *vctx, const uint8_t *data, uint32_t data_len);
+
+#endif  /* !__VERIFICATION_H__ */