pgsql: Update type-conversion documentation for long-ago changes.

Update type-conversion documentation for long-ago changes.

This example wasn't updated when we changed the behavior of bpcharlen()
in 8.0, nor when we changed the number of parameters taken by the bpchar()
cast function in 7.3. Per report from lsliang.

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/01543329514475e2c42d52891ff4245bb9f5d83c

Modified Files
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doc/src/sgml/typeconv.sgml | 22 ++++++++++++----------
1 files changed, 12 insertions(+), 10 deletions(-)