Bison 2.7.1 incorrectly claims it's version 2.7.12-4996

[Paul Eggert]

After installing Bison 2.7.1, I found that the shell command:

bison --version

outputs this text:

bison (GNU Bison) 2.7.12-4996
...

That "2.7.12-4996" isn't right; it should be "2.7.1".