*: improve multiple things e.g. making some strings.cc functions modify strings in-place, improving m4_ax_have_qt.m4 code, making anime_db.cc rely on std::optional rather than std::shared_ptr (which was stupid anyway)

<transition source="idle" target="run">
	<event name="key_up|key_shift" />
</transition>
<transition source="run" target="attack">
	<event name="key_ctrl" />
	<condition expr="weapon != null" />
</transition>