Fix a couple of includes in libloot API headers

I'll also make these changes to C++ libloot.

cxx/include/loot/exception/condition_syntax_error.h

@@ -25,7 +25,7 @@
 #ifndef LOOT_EXCEPTION_CONDITION_SYNTAX_ERROR
 #define LOOT_EXCEPTION_CONDITION_SYNTAX_ERROR
 
-#include <stdexcept>
+#include <system_error>
 
 namespace loot {
 /**

cxx/include/loot/game_interface.h

@@ -25,6 +25,7 @@
 #define LOOT_GAME_INTERFACE
 
 #include "loot/database_interface.h"
+#include "loot/enum/game_type.h"
 #include "loot/plugin_interface.h"
 
 namespace loot {