Install page misses Bison prerequisite

[Simon Sobisch]

https://gcc.gnu.org/install/prerequisites.html has a bunch of tools 
under "Tools/packages necessary for modifying GCC", but GNU Bison is 
missing.

I found it interesting to see that some files like under intl say
    1 /* A Bison parser, made from plural.y
    2    by GNU bison 1.35.  */

Not sure if that would still be able to be processed with that version 
(but it definitely has some bison3 adjustments).


Back to the issue at hand: please add Bison to the list referenced 
above, including its minimal version.

Kind regards,
Simon