Update vendor bison formula to 3.2+patches

[drbenmorgan]

Please follow the general troubleshooting steps first:

• [x] Ran brew update and retried your prior step?
• [x] Ran brew doctor, fixed as many issues as possible and retried your prior step?
• [x] Confirmed this is a problem with specific formulae and not brew? If it's a general brew problem please file this issue at https://github.com/supernemo-dbd/brew/issues/new

You can erase any parts of this template not applicable to your Issue.

Formula Requests:

Bison 3.2 is broken on build-from-source on CentOS6. Vendored 3.1 won't meet requirements in brew for upstream flex. Will need to vendor 3.2 and apply upstream patches, or add HEAD/devel option.