top: add more robustness to logic for reading a rcfile

At this point I don't know if the Rc.id ever carried a
value of 'b', 'c', 'd' or 'e' in a public release. But
I do know that those values ought not to be recognized
in any configuration file. Now they won't be for sure.

[ the net result is that now a user with such a file ]
[ will see the 'incompatible rcfile' message instead ]
[ of that misleading 'window entry corrupt' message. ]

Signed-off-by: Jim Warner <james.warner@comcast.net>

top/top.c

@@ -3824,6 +3824,8 @@ static const char *configs_file (FILE *fp, const char *name, float *delay) {
    }
    if (Rc.id < 'a' || Rc.id > RCF_VERSION_ID)
       return p;
+   if (strchr("bcde", Rc.id))
+      return p;
    if (Rc.mode_altscr < 0 || Rc.mode_altscr > 1)
       return p;
    if (Rc.mode_irixps < 0 || Rc.mode_irixps > 1)