Tweak bison build rules so that we get the same error messages from

Tweak bison build rules so that we get the same error messages from
bison 1.875 and later as we did from earlier bison releases.  Eventually
we will probably want to adopt the newer message spelling ... but not yet.
Per recent discussion on pgpatches.
Note: I didn't change the build rules for bootstrap, ecpg, or plpgsql
grammars, since these do not affect regression test results.