De-duplicate stuck prevention for the player/SCM

Stuck prevention (pushing the player/supercrewmate out if they are
inside a wall) has been factored out into its own function, so it's no
longer copy-pasted but slightly tweaked just for the supercrewmate.

desktop_version/src/Entity.h

@@ -160,6 +160,8 @@ public:
 
     void collisioncheck(int i, int j, bool scm = false);
 
+    void stuckprevention(int t);
+
 
     std::vector<entclass> entities;