Fix bogus %name-prefix option syntax in all our Bison files.

%name-prefix doesn't use an "=" sign according to the Bison docs, but it
silently accepted one anyway, until Bison 3.0.  This was originally a
typo of mine in commit 012abebab1, and we
seem to have slavishly copied the error into all the other grammar files.

Per report from Vik Fearing; analysis by Peter Eisentraut.

Back-patch to all active branches, since somebody might try to build
a back branch with up-to-date tools.

src/test/isolation/specparse.y

@@ -20,7 +20,7 @@ TestSpec		parseresult;			/* result of parsing is left here */
 %}
 
 %expect 0
-%name-prefix="spec_yy"
+%name-prefix "spec_yy"
 
 %union
 {