pgsql: A few trivial code cleanups motivated by reading warnings

Log Message:
-----------
A few trivial code cleanups motivated by reading warnings generated
by a recent HP C compiler.  Mostly, get rid of useless local variables
that are assigned to but never used.

Modified Files:
--------------
    pgsql/src/backend/access/gist:
        gist.c (r1.126 -> r1.127)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gist.c.diff?r1=1.126&r2=1.127)
    pgsql/src/backend/access/hash:
        hashinsert.c (r1.38 -> r1.39)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hashinsert.c.diff?r1=1.38&r2=1.39)
        hashsearch.c (r1.40 -> r1.41)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hashsearch.c.diff?r1=1.40&r2=1.41)
    pgsql/src/backend/access/nbtree:
        nbtsearch.c (r1.95 -> r1.96)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtsearch.c.diff?r1=1.95&r2=1.96)
        nbtutils.c (r1.64 -> r1.65)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtutils.c.diff?r1=1.64&r2=1.65)
        nbtxlog.c (r1.23 -> r1.24)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtxlog.c.diff?r1=1.23&r2=1.24)
    pgsql/src/backend/catalog:
        heap.c (r1.291 -> r1.292)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/heap.c.diff?r1=1.291&r2=1.292)
        pg_conversion.c (r1.27 -> r1.28)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_conversion.c.diff?r1=1.27&r2=1.28)
    pgsql/src/backend/commands:
        typecmds.c (r1.81 -> r1.82)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/typecmds.c.diff?r1=1.81&r2=1.82)
    pgsql/src/backend/executor:
        nodeHashjoin.c (r1.74 -> r1.75)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeHashjoin.c.diff?r1=1.74&r2=1.75)
    pgsql/src/backend/rewrite:
        rewriteDefine.c (r1.106 -> r1.107)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/rewrite/rewriteDefine.c.diff?r1=1.106&r2=1.107)