user specified that one of her tokens is numbered 256, then error
will be mapped onto another number.
+* Error recovery now conforms to documentation and to POSIX
+ When a Bison-generated parser encounters a syntax error, it now pops
+ the stack until it finds a state that allows shifting the error
+ token. Formerly, it popped the stack until it found a state that
+ allowed some non-error action other than a default reduction on the
+ error token. The new behavior has long been the documented behavior,
+ and has long been required by POSIX. For more details, please see
+ <http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
+
* Large grammars
Large grammars are now supported (large token numbers, large grammar
size (= sum of the LHS and RHS lengths), large LALR tables).