first attempt to port fix halt to minimizations

doc/src/fix_halt.txt

@@ -135,8 +135,7 @@ files"_restart.html.  None of the "fix_modify"_fix_modify.html options
 are relevant to this fix.  No global or per-atom quantities are stored
 by this fix for access by various "output commands"_Howto_output.html.
 No parameter of this fix can be used with the {start/stop} keywords of
-the "run"_run.html command.  This fix is not invoked during "energy
-minimization"_minimize.html.
+the "run"_run.html command.
 
 [Restrictions:] none
 

src/fix_halt.cpp

@@ -143,6 +143,13 @@ void FixHalt::init()
 
 /* ---------------------------------------------------------------------- */
 
+void FixHalt::min_step(double, double *)
+{
+  if ((update->ntimestep % nevery) == 0) end_of_step();
+}
+
+/* ---------------------------------------------------------------------- */
+
 void FixHalt::end_of_step()
 {
   // variable evaluation may invoke computes so wrap with clear/add

src/fix_halt.h

@@ -32,6 +32,7 @@ class FixHalt : public Fix {
   int setmask();
   void init();
   void end_of_step();
+  void min_step(double, double *);
   void post_run();
 
  private: