Destructor cleanups and regularization among the three skeletons.

Destructor cleanups and regularization among the three skeletons.
* NEWS: Document the behavior changes.
* data/glr.c (yyrecoverSyntaxError): Don't bother to pop the
stack before failing, as the cleanup code will do it for us now.
* data/lalr1.cc (yyerrlab): Likewise.
* data/glr.c (yyparse): Pop everything off the stack before
freeing it, so that destructors get called properly.
* data/lalr1.cc (yyreturn): Likewise.
* data/yacc.c (yyreturn): Pop and destroy the start symbol, too.
This is more consistent.
* doc/bison.texinfo (Destructor Decl): Mention more reasons
why destructors might be called.  1.875 -> 2.1.
(Destructor Decl, Decl Summary, Table of Symbols):
Some English-language cleanups for %destructor.
* tests/actions.at (_AT_CHECK_PRINTER_AND_DESTRUCTOR):
Add output line for destructor of start symbol.
* tests/calc.at (AT_CHECK_CALC): Add one to line counts,
because of that same extra output line.