jsonb is also breaking the rule against nameless unions

Same issue as in
http://www.postgresql.org/message-id/31718.1394059256@sss.pgh.pa.us

In file included from jsonb.c:19:
../../../../src/include/utils/jsonb.h:195: warning: unnamed struct/union that defines no instances
jsonb.c: In function `jsonb_in_object_field_start':
jsonb.c:250: structure has no member named `string'
jsonb.c:251: structure has no member named `string'
jsonb.c:251: structure has no member named `string'
jsonb.c:252: structure has no member named `string'
jsonb.c: In function `jsonb_put_escaped_value':
jsonb.c:266: structure has no member named `string'
jsonb.c:266: structure has no member named `string'
jsonb.c:271: structure has no member named `numeric'
jsonb.c:274: structure has no member named `boolean'
jsonb.c: In function `jsonb_in_scalar':
jsonb.c:301: structure has no member named `string'
jsonb.c:302: structure has no member named `string'
jsonb.c:302: structure has no member named `string'
jsonb.c:303: structure has no member named `string'
... etc etc etc ...

We really need to get a buildfarm member going that complains about this.
I had hoped to install a sufficiently old gcc version on prairiedog or
dromedary, but didn't have much luck rebuilding ancient gcc releases on
OS X.
        regards, tom lane