Fixed missing includes

src/engine.c

@@ -65,6 +65,7 @@
 #include "equation_of_state.h"
 #include "error.h"
 #include "feedback.h"
+#include "fof.h"
 #include "gravity.h"
 #include "gravity_cache.h"
 #include "hydro.h"

src/engine_fof.c

@@ -25,6 +25,9 @@
 /* This object's header. */
 #include "engine.h"
 
+/* Local headers. */
+#include "fof.h"
+
 /**
  * @brief Activate all the #gpart communications in preparation
  * fof a call to FOF.

src/runner_others.c

@@ -45,6 +45,7 @@
 #include "engine.h"
 #include "error.h"
 #include "feedback.h"
+#include "fof.h"
 #include "gravity.h"
 #include "hydro.h"
 #include "logger.h"