Permission: split permission "player" from "control"

Some users want certain clients to fully control playback, but do not
want them to be able to trigger database update.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1124

src/Permission.cxx

@@ -41,6 +41,7 @@ static constexpr struct {
 } permission_names[] = {
 	{ "read", PERMISSION_READ },
 	{ "add", PERMISSION_ADD },
+	{ "player", PERMISSION_PLAYER },
 	{ "control", PERMISSION_CONTROL },
 	{ "admin", PERMISSION_ADMIN },
 	{ nullptr, 0 },
@@ -75,6 +76,11 @@ static unsigned parsePermissions(const char *string)
 		if (!i.empty())
 			permission |= ParsePermission(i);
 
+	/* for backwards compatiblity with MPD 0.22 and older,
+	   "control" implies "play" */
+	if (permission & PERMISSION_CONTROL)
+		permission |= PERMISSION_PLAYER;
+
 	return permission;
 }