Support overclocking and underclocking the Gamecube CPU

Won't work with all games, but provides a nice way to spend extra CPU to make
a variable framerate game faster (e.g. Spyro or The Last Story), or to make
a game use less CPU at the cost of a lower framerate (e.g. Rogue Leader).

Source/Core/Common/StringUtil.h

@@ -64,6 +64,8 @@ template <typename N>
 static bool TryParse(const std::string &str, N *const output)
 {
 	std::istringstream iss(str);
+	// is this right? not doing this breaks reading floats on locales that use different decimal separators
+	iss.imbue(std::locale(".1252"));
 
 	N tmp = 0;
 	if (iss >> tmp)