make QUICKHOME configureable

Marlin/Configuration.h

 #define X_HOME_RETRACT_MM 5 
 #define Y_HOME_RETRACT_MM 5 
 #define Z_HOME_RETRACT_MM 1 
+#define QUICK_HOME  //if this is defined, if both x and y are to be homed, a diagonal move will be performed initially.
 
 #define AXIS_RELATIVE_MODES {false, false, false, false}
 

Marlin/Marlin.pde

       }
       feedrate = 0.0;
       home_all_axis = !((code_seen(axis_codes[0])) || (code_seen(axis_codes[1])) || (code_seen(axis_codes[2])));
-      
+      #ifdef QUICK_HOME
       if( code_seen(axis_codes[0]) && code_seen(axis_codes[1]) )  //first diagonal move
       {
         current_position[X_AXIS] = 0; current_position[Y_AXIS] = 0;
         prepare_move();
         current_position[X_AXIS] = 0; current_position[Y_AXIS] = 0;
       }
+      #endif
       
       if((home_all_axis) || (code_seen(axis_codes[X_AXIS]))) 
       {