pgsql: Work around a subtle portability problem in use of printf %s

Log Message:
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Work around a subtle portability problem in use of printf %s format.
Depending on which spec you read, field widths and precisions in %s may be
counted either in bytes or characters. Our code was assuming bytes, which
is wrong at least for glibc's implementation, and in any case libc might
have a different idea of the prevailing encoding than we do. Hence, for
portable results we must avoid using anything more complex than just "%s"
unless the string to be printed is known to be all-ASCII.

This patch fixes the cases I could find, including the psql formatting
failure reported by Hernan Gonzalez. In HEAD only, I also added comments
to some places where it appears safe to continue using "%.*s".

Tags:
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REL8_1_STABLE

Modified Files:
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pgsql/src/backend/parser:
scansup.c (r1.30 -> r1.30.2.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/scansup.c?r1=1.30&r2=1.30.2.1)
pgsql/src/backend/utils/error:
elog.c (r1.167.2.9 -> r1.167.2.10)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/error/elog.c?r1=1.167.2.9&r2=1.167.2.10)
pgsql/src/interfaces/libpq:
fe-misc.c (r1.122.2.1 -> r1.122.2.2)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-misc.c?r1=1.122.2.1&r2=1.122.2.2)