bison-2.4.1 with more graph output

[tys lefering]

hi,
very easy ported the vcg graph output drivers
from bison-2.3a into the bison-2.4.1 version.
now there is a choice of graph output to use.

when using 'bison -g parser.y' then it generates
both dot and vcg graph output and when a filename
is specified using 'bison --graph=filename parser.y'
then it generates only dot output.

made a bison-2.4.1-vcg.tar.gz if someone
is interested. can also generate the diffs.

best regards,
tys lefering.