treewide: fix #include errors after gcc-5.4

They were mostly missing <cmath> or <math.h>.

pkgs/games/the-butterfly-effect/default.nix

@@ -9,8 +9,12 @@ stdenv.mkDerivation rec {
     sha256 = "1cs4q9qiakfd2m1lvfsvfgf8yvhxzmc06glng5d80piwyn6ymzxg";
   };
 
+  postPatch = "sed '1i#include <vector>' -i src/model/World.h";
+
   buildInputs = [ qt4 box2d which cmake ];
 
+  enableParallelBuilding = true;
+
   installPhase = ''
     make DESTDIR=.. install
     mkdir -p $out/bin