Clean up getTime helpers

This increases size of the getTime return values to 64 bits.
It also removes the TimeGetter classes since the getTime functions
are now very precise.

src/guiFormSpecMenu.h

@@ -421,7 +421,7 @@ protected:
 	gui::IGUIStaticText *m_tooltip_element;
 
 	u32 m_tooltip_show_delay;
-	s32 m_hovered_time;
+	s64 m_hovered_time;
 	s32 m_old_tooltip_id;
 	std::wstring m_old_tooltip;
 
@@ -527,7 +527,7 @@ private:
 	struct clickpos
 	{
 		v2s32 pos;
-		s32 time;
+		s64 time;
 	};
 	clickpos m_doubleclickdetect[2];