system/Event{FD,Pipe}: add "noexcept"

src/system/EventFD.hxx

@@ -35,7 +35,7 @@ public:
 	 */
 	EventFD();
 
-	int Get() const {
+	int Get() const noexcept {
 		return fd.Get();
 	}
 
@@ -43,13 +43,13 @@ public:
 	 * Checks if Write() was called at least once since the last
 	 * Read() call.
 	 */
-	bool Read();
+	bool Read() noexcept;
 
 	/**
 	 * Wakes up the reader.  Multiple calls to this function will
 	 * be combined to one wakeup.
 	 */
-	void Write();
+	void Write() noexcept;
 };
 
 #endif