Byacc not used when Bison not available

[David O'Brien]

egcs*/configure and egcs*/gcc/configure correctly searches for byacc and
then yacc if bison is not available.  Problem is somewhere after this
point, yacc is not passed down thru the Makefiles if it is to be used
over bison.

This is easy to reproduce on a Linux system by simply renaming bison to
byacc and then looking at the full output from ``make bootstrap''.

[ note there is an inconsistency between egcs*/configure and
egcs*/gcc/configure, where the former searches for "'bison -y' byacc
yacc" and the later only for "'bison -y' byacc" ]

-- 
-- David    (obrien@NUXI.com)