Revert "Added nhassert to core."

This reverts commit 0ca299acb3.

sys/winnt/winnt.c

@@ -475,6 +475,16 @@ char *buf;
 }
 #endif /* RUNTIME_PORT_ID */
 
+/* nhassert_failed is called when an nhassert's condition is false */
+void nhassert_failed(const char * exp, const char * file, int line)
+{
+    char message[BUFSZ];
+    snprintf(message, sizeof(message),
+                "NHASSERT(%s) in '%s' at line %d", exp, file, line);
+
+    impossible(message);
+}
+
 void
 nethack_exit(code)
 int code;