Fix 1998/schnitzi for linux

It segfaulted due to wrong type of a variable.

It still crashes under macOS which I will be looking at in the near
future but it at least works for linux.

I noted in the bugs.md a compiler warning that should not be changed as
it's not a bug and in fact 'fixing' it will introduce a bug.

1998/schnitzi/Makefile

@@ -97,7 +97,7 @@ CDEFINE=
 
 # Include files that are needed to compile
 #
-CINCLUDE=
+CINCLUDE= -include stdlib.h
 #CINCLUDE= -include stdlib.h
 #CINCLUDE= -include stdio.h
 #CINCLUDE= -include stdlib.h -include stdio.h