Note: This diff is for Nethack 3.4.0 which is already OUTDATED.
For newer game versions I have included the functionality in the makedefs
diff ( http://www.iki.fi/jslahti/nethack.html#makedefs ).
I recommend using the newest version of the source instead of still 
compiling  3.4.0.

*** src/version.c.off	Thu Mar 21 01:43:20 2002
--- src/version.c	Sun Apr 28 18:49:48 2002
***************
*** 14,19 ****
--- 14,27 ----
  #include "patchlevel.h"
  #endif
  
+ /* Features to be ignored for checking version compatibility (JL): 
+  * 23 TIMED_DELAY
+  * 21 SCORE_ON_BOTL
+  * 20 EXP_ON_BOTL
+  * 17 TEXTCOLOR 
+  */
+ #define FEATURE_MASK 1L << 23 | 1L << 21 | 1L << 20 | 1L << 17 
+  
  /* fill and return the given buffer with the nethack version string */
  char *
  getversionstring(buf)
***************
*** 64,70 ****
  	    if (complain)
  		pline("Version mismatch for file \"%s\".", filename);
  	    return FALSE;
! 	} else if (version_data->feature_set != VERSION_FEATURES ||
  		   version_data->entity_count != VERSION_SANITY1 ||
  		   version_data->struct_sizes != VERSION_SANITY2) {
  	    if (complain)
--- 72,84 ----
  	    if (complain)
  		pline("Version mismatch for file \"%s\".", filename);
  	    return FALSE;
! 	} else if (
! #ifdef FEATURE_MASK
! 		   (version_data->feature_set | FEATURE_MASK) !=
! 		   (VERSION_FEATURES | FEATURE_MASK) ||
! #else
! 		   version_data->feature_set != VERSION_FEATURES ||
! #endif
  		   version_data->entity_count != VERSION_SANITY1 ||
  		   version_data->struct_sizes != VERSION_SANITY2) {
  	    if (complain)
***************
*** 72,77 ****
--- 86,95 ----
  		      filename);
  	    return FALSE;
  	}
+ #ifdef FEATURE_MASK
+ 	else if (complain && version_data->feature_set != VERSION_FEATURES)
+ 	    pline("Slightly different features in file \"%s\".", filename); 
+ #endif
  	return TRUE;
  }