* NEWS: Bison-generated parsers no longer default to using the

* NEWS: Bison-generated parsers no longer default to using the
alloca function (when available) to extend the parser stack, due
to widespread problems in unchecked stack-overflow detection.
* data/glr.c (YYMAXDEPTH): Remove undef when zero.  It's the user's
responsibility to set it to a positive value.  This lets the user
specify a value that is not a preprocessor constant.
* data/yacc.c (YYMAXDEPTH): Likewise.
(YYSTACK_ALLOC): Define only if YYSTACK_USE_ALLOCA is nonzero.
* doc/bison.texinfo (Stack Overflow): YYMAXDEPTH no longer needs
to be a compile-time constant.  However, explain the constraints on it.
Also, explain the constraints on YYINITDEPTH.
(Table of Symbols): Explain that alloca is no longer the default.
Explain the user's responsibility if they define YYSTACK_USE_ALLOCA
to 1.