pgsql: Fix man page markup for with multiple variants

Fix man page markup for <cmdsynopsis> with multiple variants

Command synopses using <cmdsynopsis> with multiple variants previously used
<sbr> to break lines between variants.  The new man page toolchain introduced
in 9.0 makes a mess out of that, and that markup was probably wrong all along,
because <sbr> is supposed to break lines within a synopsis, not between them.
So fix that by using multiple <cmdsynopsis> elements inside <refsynopsisdiv>.

backpatched to 9.0

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=635de8365f0299cfa2db24c56abcfccb65d020f0

Modified Files
--------------
doc/src/sgml/ref/clusterdb.sgml  |    4 +++-
doc/src/sgml/ref/createlang.sgml |    4 +++-
doc/src/sgml/ref/droplang.sgml   |    4 +++-
doc/src/sgml/ref/pg_ctl-ref.sgml |   26 ++++++++++++++++----------
doc/src/sgml/ref/reindexdb.sgml  |    8 ++++++--
doc/src/sgml/ref/vacuumdb.sgml   |    4 +++-
6 files changed, 34 insertions(+), 16 deletions(-)