General: Clean up inclusions

Ensures that each header includes all of its dependencies that can't be
forward declared.

lib/SongConverter.cpp

@@ -1,9 +1,13 @@
 #include "amuse/SongConverter.hpp"
-#include "amuse/SongState.hpp"
-#include "amuse/Common.hpp"
+
+#include <algorithm>
+#include <array>
 #include <cstdlib>
 #include <map>
 
+#include "amuse/Common.hpp"
+#include "amuse/SongState.hpp"
+
 namespace amuse {
 
 constexpr uint8_t clamp7(uint8_t val) { return std::max(0, std::min(127, int(val))); }