'struct former' -> 'struct ebones'

Some variants were already using a similar approach
using a struct called 'ebones', so adopt the same naming
so NetHack-3.7, hardfought, and some variants are using
the same name.

As before there are fields in the struct that are not
currently used by NetHack-3.7, but the intent is that
hardfought save and bones files can be loaded by
NetHack-3.7 without code modification, for debugging
bug reports.

This invalidates existing save and bones files.

include/hack.h

@@ -767,6 +767,7 @@ struct role_filter {
     boolean roles[NUM_ROLES + 1];
     short mask;
 };
+#define NUM_RACES (5)
 
 enum saveformats {
     invalid = 0,