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

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

src/decoder/plugins/GmeDecoderPlugin.cxx

@@ -74,7 +74,7 @@ gme_plugin_init(gcc_unused const ConfigBlock &block)
 
 gcc_pure
 static unsigned
-ParseSubtuneName(const char *base)
+ParseSubtuneName(const char *base) noexcept
 {
 	if (memcmp(base, SUBTUNE_PREFIX, sizeof(SUBTUNE_PREFIX) - 1) != 0)
 		return 0;