Rework internal module registration to happen in constructors.

src/modules/system/sdl/System.cpp

@@ -39,14 +39,10 @@ namespace sdl
 {
 
 System::System()
+	: love::system::System("love.system.sdl")
 {
 }
 
-const char *System::getName() const
-{
-	return "love.system.sdl";
-}
-
 int System::getProcessorCount() const
 {
 	return SDL_GetCPUCount();

src/modules/system/sdl/System.h

@@ -42,9 +42,6 @@ public:
 	System();
 	virtual ~System() {}
 
-	// Implements Module.
-	const char *getName() const override;
-
 	int getProcessorCount() const override;
 
 	void setClipboardText(const std::string &text) const override;