%printer: support both yyo and yyoutput.

%printer: support both yyo and yyoutput.

lalr1.cc used to support yyo, but not yyoutput.  Support both,
but document only yyoutput (at least until there is some consensus
on this).

* data/c.m4 (yy_symbol_value_print): Also support yyo.
* data/glr.cc  (yy_symbol_value_print_): Support both yyo and yyoutput.
* data/lalr1.cc: Also support yyoutput.
* doc/bison.texinfo: Explicitly use yyoutput in the examples.
* examples/mfcalc/mfcalc.test: Test the -p option.