Move most /contrib README files into SGML. Some still need conversion

or will never be converted.

contrib/btree_gist/README.btree_gist

@@ -1,55 +0,0 @@
-This is a B-Tree implementation using GiST that supports the int2, int4,
-int8, float4, float8 timestamp with/without time zone, time
-with/without time zone, date, interval, oid, money, macaddr, char,
-varchar/text, bytea, numeric, bit, varbit and inet/cidr types.
-
-All work was done by Teodor Sigaev (teodor@stack.net) , Oleg Bartunov
-(oleg@sai.msu.su), Janko Richter (jankorichter@yahoo.de).
-See http://www.sai.msu.su/~megera/postgres/gist for additional
-information.
-
-NEWS:
-
-     Apr 17, 2004 - Performance optimizing
-
-     Jan 21, 2004 - add support for bytea, numeric, bit, varbit, inet/cidr
-
-     Jan 17, 2004 - Reorganizing code and add support for char, varchar/text
-
-     Jan 10, 2004 - btree_gist now support oid , timestamp with time zone ,
-                    time with and without time zone, date , interval
-                    money, macaddr
-
-     Feb  5, 2003 - btree_gist now support int2, int8, float4, float8
-     
-NOTICE:
-     This version will only work with PostgreSQL version 7.4 and above
-     because of changes in the system catalogs and the function call
-     interface.
-     
-     If you want to index varchar attributes, you have to index using
-     the function text(<varchar>):
-     Example:
-       CREATE TABLE test ( a varchar(23) );
-       CREATE INDEX testidx ON test USING GIST ( text(a) );
-
-
-INSTALLATION:
-
-  gmake
-  gmake install
-  -- load functions
-  psql <database> < btree_gist.sql
-
-REGRESSION TEST:
-
-   gmake installcheck
-
-EXAMPLE USAGE:
-
-   create table test (a int4);
-   -- create index
-   create index testidx on test using gist (a);
-   -- query
-   select * from test where a < 10;
-