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/interfaces/ecpg/preproc/ecpg.header

@@ -572,7 +572,7 @@ add_typedef(char *name, char *dimension, char *length, enum ECPGttype type_enum,
 %}
 
 %expect 0
-%name-prefix="base_yy"
+%name-prefix "base_yy"
 %locations
 
 %union {