pgsql: Add thesaurus dictionary which can replace N>0 lexemes by M>0

Log Message:
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Add thesaurus dictionary which can replace N>0 lexemes by M>0 lexemes.
It required some changes in lexize algorithm, but interface with
dictionaries stays compatible with old dictionaries.

Funded by Georgia Public Library Service and LibLime, Inc.

Modified Files:
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pgsql/contrib/tsearch2:
Makefile (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/Makefile.diff?r1=1.14&r2=1.15)
common.c (r1.5 -> r1.6)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/common.c.diff?r1=1.5&r2=1.6)
common.h (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/common.h.diff?r1=1.4&r2=1.5)
dict.c (r1.11 -> r1.12)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/dict.c.diff?r1=1.11&r2=1.12)
dict.h (r1.6 -> r1.7)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/dict.h.diff?r1=1.6&r2=1.7)
stopword.c (r1.7 -> r1.8)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/stopword.c.diff?r1=1.7&r2=1.8)
ts_cfg.c (r1.18 -> r1.19)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/ts_cfg.c.diff?r1=1.18&r2=1.19)
tsearch.sql.in (r1.18 -> r1.19)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/tsearch.sql.in.diff?r1=1.18&r2=1.19)
untsearch.sql.in (r1.6 -> r1.7)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/untsearch.sql.in.diff?r1=1.6&r2=1.7)
pgsql/contrib/tsearch2/expected:
tsearch2.out (r1.20 -> r1.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/expected/tsearch2.out.diff?r1=1.20&r2=1.21)

Added Files:
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pgsql/contrib/tsearch2:
dict_thesaurus.c (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/dict_thesaurus.c?rev=1.1&content-type=text/x-cvsweb-markup)
thesaurus (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/thesaurus?rev=1.1&content-type=text/x-cvsweb-markup)
ts_lexize.c (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/ts_lexize.c?rev=1.1&content-type=text/x-cvsweb-markup)