output/Interface: allow Pause() to throw exception

Coverity discovered that the Pulse plugin could throw exceptions from
Pause(), but that method was marked "noexcept" because its caller was
not designed to catch exceptions.  So instead of avoiding exceptions
(by catching and logging them in each and every implementation), let's
allow them, and do the catch/log game in the MPD core.

src/output/plugins/JackOutputPlugin.cxx

@@ -135,7 +135,7 @@ struct JackOutput final : AudioOutput {
 
 	size_t Play(const void *chunk, size_t size) override;
 
-	bool Pause() noexcept override;
+	bool Pause() override;
 };
 
 static constexpr Domain jack_output_domain("jack_output");
@@ -661,7 +661,7 @@ JackOutput::Play(const void *chunk, size_t size)
 }
 
 inline bool
-JackOutput::Pause() noexcept
+JackOutput::Pause()
 {
 	if (shutdown)
 		return false;