pgsql-server: Add index mention: <P>In pre-8.0 releases, indexes

Log Message:
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Add index mention:

<P>In pre-8.0 releases, indexes often can not be used unless the data
types exactly match the index's column types. This is particularly
true of int2, int8, and numeric column indexes.</P>

Modified Files:
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pgsql-server/doc:
FAQ (r1.268 -> r1.269)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/FAQ.diff?r1=1.268&amp;r2=1.269)
pgsql-server/doc/src/FAQ:
FAQ.html (r1.226 -> r1.227)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/FAQ/FAQ.html.diff?r1=1.226&amp;r2=1.227)