system/SignalFD: add "noexcept"

src/system/SignalFD.cxx

@@ -33,7 +33,7 @@ SignalFD::Create(const sigset_t &mask)
 }
 
 int
-SignalFD::Read()
+SignalFD::Read() noexcept
 {
 	assert(fd.IsDefined());
 

src/system/SignalFD.hxx

@@ -39,11 +39,11 @@ public:
 	 */
 	void Create(const sigset_t &mask);
 
-	void Close() {
+	void Close() noexcept {
 		fd.Close();
 	}
 
-	int Get() const {
+	int Get() const noexcept {
 		return fd.Get();
 	}
 
@@ -52,7 +52,7 @@ public:
 	 * signal number on success or -1 if there are no more
 	 * signals.
 	 */
-	int Read();
+	int Read() noexcept;
 };
 
 #endif