pgsql: Change typedef struct {} WordEntryPos; to typedef uint16

Log Message:
-----------
Change
typedef struct {} WordEntryPos;
to
typedef uint16 WordEntryPos
according to http://www.pgsql.ru/db/mw/msg.html?mid=2035188

Require re-fill all tsvector fields and reindex tsvector indexes.

Modified Files:
--------------
    pgsql/contrib/tsearch2:
        query.c (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/query.c.diff?r1=1.11&r2=1.12)
        rank.c (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/rank.c.diff?r1=1.5&r2=1.6)
        ts_stat.c (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/ts_stat.c.diff?r1=1.9&r2=1.10)
        tsvector.c (r1.12 -> r1.13)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/tsvector.c.diff?r1=1.12&r2=1.13)
        tsvector.h (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/tsvector.h.diff?r1=1.3&r2=1.4)
        tsvector_op.c (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/tsvector_op.c.diff?r1=1.3&r2=1.4)