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

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

test/dump_rva2.cxx

@@ -40,7 +40,7 @@
 
 const char *
 config_get_string(gcc_unused enum ConfigOption option,
-		  const char *default_value)
+		  const char *default_value) noexcept
 {
 	return default_value;
 }

test/read_mixer.cxx

@@ -33,7 +33,7 @@
 #include <stdlib.h>
 
 const FilterPlugin *
-filter_plugin_by_name(gcc_unused const char *name)
+filter_plugin_by_name(gcc_unused const char *name) noexcept
 {
 	assert(false);
 	return NULL;

test/run_output.cxx

@@ -55,7 +55,7 @@ public:
 };
 
 const FilterPlugin *
-filter_plugin_by_name(gcc_unused const char *name)
+filter_plugin_by_name(gcc_unused const char *name) noexcept
 {
 	assert(false);
 	return NULL;

test/test_rewind.cxx

@@ -32,7 +32,7 @@ public:
 	}
 
 	/* virtual methods from InputStream */
-	bool IsEOF() override {
+	bool IsEOF() noexcept override {
 		return remaining == 0;
 	}
 

test/test_translate_song.cxx

@@ -32,7 +32,7 @@ Log(const Domain &domain, gcc_unused LogLevel level, const char *msg)
 }
 
 bool
-uri_supported_scheme(const char *uri)
+uri_supported_scheme(const char *uri) noexcept
 {
 	return strncmp(uri, "http://", 7) == 0;
 }
@@ -130,13 +130,13 @@ DetachedSong::LoadFile(Path path)
 }
 
 const Database *
-Client::GetDatabase() const
+Client::GetDatabase() const noexcept
 {
 	return reinterpret_cast<const Database *>(this);
 }
 
 const Storage *
-Client::GetStorage() const
+Client::GetStorage() const noexcept
 {
 	return ::storage;
 }