*: add "noexcept" to many, many function prototypes

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

src/db/plugins/upnp/Directory.hxx

@@ -40,7 +40,7 @@ public:
 	~UPnPDirContent();
 
 	gcc_pure
-	UPnPDirObject *FindObject(const char *name) {
+	UPnPDirObject *FindObject(const char *name) noexcept {
 		for (auto &o : objects)
 			if (o.name == name)
 				return &o;