pgsql: Fix core dump with buffer-overrun by too long infinitive.

Log Message:
-----------
Fix core dump with buffer-overrun by too long infinitive. Add checking of using
fixed length arrays to prevent array's overrun. Per report by
Hannes Dorbath <light@theendofthetunnel.de> and comments by Tom.

Modified Files:
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    pgsql/src/backend/tsearch:
        spell.c (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tsearch/spell.c?r1=1.9&r2=1.10)