Lower the size of the module_t structure because not any module as more than...

Lower the size of the module_t structure because not any module as more than 15 shortcut (I choose 20 to be safe)

Thanks to Pierre d'Herbemont who pointed this out.

src/modules/modules.h

@@ -69,7 +69,7 @@ struct module_cache_t
 };
 
 
-#define MODULE_SHORTCUT_MAX 50
+#define MODULE_SHORTCUT_MAX 20
 
 /* The module handle type. */
 #if defined(HAVE_DL_DYLD) && !defined(__x86_64__)