pgsql: Remove references to READMEs from /contrib Makefiles.

Log Message:
-----------
Remove references to READMEs from /contrib Makefiles.

Modified Files:
--------------
    pgsql/contrib/adminpack:
        Makefile (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/adminpack/Makefile?r1=1.5&r2=1.6)
    pgsql/contrib/btree_gist:
        Makefile (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/btree_gist/Makefile?r1=1.11&r2=1.12)
    pgsql/contrib/chkpass:
        Makefile (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/chkpass/Makefile?r1=1.9&r2=1.10)
    pgsql/contrib/cube:
        Makefile (r1.20 -> r1.21)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/cube/Makefile?r1=1.20&r2=1.21)
    pgsql/contrib/dblink:
        Makefile (r1.14 -> r1.15)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/dblink/Makefile?r1=1.14&r2=1.15)
    pgsql/contrib/earthdistance:
        Makefile (r1.18 -> r1.19)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/earthdistance/Makefile?r1=1.18&r2=1.19)
    pgsql/contrib/fuzzystrmatch:
        Makefile (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/fuzzystrmatch/Makefile?r1=1.9&r2=1.10)
    pgsql/contrib/hstore:
        Makefile (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/hstore/Makefile?r1=1.5&r2=1.6)
    pgsql/contrib/intagg:
        Makefile (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/intagg/Makefile?r1=1.8&r2=1.9)
    pgsql/contrib/intarray:
        Makefile (r1.15 -> r1.16)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/intarray/Makefile?r1=1.15&r2=1.16)
    pgsql/contrib/isn:
        Makefile (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/isn/Makefile?r1=1.2&r2=1.3)
    pgsql/contrib/lo:
        Makefile (r1.16 -> r1.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/lo/Makefile?r1=1.16&r2=1.17)
    pgsql/contrib/ltree:
        Makefile (r1.7 -> r1.8)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/Makefile?r1=1.7&r2=1.8)
    pgsql/contrib/oid2name:
        Makefile (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/oid2name/Makefile?r1=1.9&r2=1.10)
    pgsql/contrib/pageinspect:
        Makefile (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pageinspect/Makefile?r1=1.2&r2=1.3)
    pgsql/contrib/pg_buffercache:
        Makefile (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_buffercache/Makefile?r1=1.4&r2=1.5)
    pgsql/contrib/pg_freespacemap:
        Makefile (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_freespacemap/Makefile?r1=1.3&r2=1.4)
    pgsql/contrib/pg_standby:
        Makefile (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_standby/Makefile?r1=1.3&r2=1.4)
    pgsql/contrib/pg_trgm:
        Makefile (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pg_trgm/Makefile?r1=1.8&r2=1.9)
    pgsql/contrib/pgbench:
        Makefile (r1.15 -> r1.16)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgbench/Makefile?r1=1.15&r2=1.16)
    pgsql/contrib/pgcrypto:
        Makefile (r1.26 -> r1.27)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgcrypto/Makefile?r1=1.26&r2=1.27)
    pgsql/contrib/pgrowlocks:
        Makefile (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgrowlocks/Makefile?r1=1.4&r2=1.5)
    pgsql/contrib/pgstattuple:
        Makefile (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgstattuple/Makefile?r1=1.8&r2=1.9)
    pgsql/contrib/seg:
        Makefile (r1.19 -> r1.20)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/seg/Makefile?r1=1.19&r2=1.20)
    pgsql/contrib/sslinfo:
        Makefile (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/sslinfo/Makefile?r1=1.9&r2=1.10)
    pgsql/contrib/tablefunc:
        Makefile (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tablefunc/Makefile?r1=1.8&r2=1.9)
    pgsql/contrib/uuid-ossp:
        Makefile (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/uuid-ossp/Makefile?r1=1.2&r2=1.3)
    pgsql/contrib/vacuumlo:
        Makefile (r1.16 -> r1.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/vacuumlo/Makefile?r1=1.16&r2=1.17)
    pgsql/contrib/xml2:
        Makefile (r1.10 -> r1.11)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/xml2/Makefile?r1=1.10&r2=1.11)