pgsql: Properly escape usernames in initdb, so names with single-quotes

Properly escape usernames in initdb, so names with single-quotes are
supported. Also add assert to catch future breakage.

Also, improve documentation that "double"-quotes must be used in
pg_hba.conf (not single quotes).

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/a973296598f2d1eec48138a2ce4f3e63410d9ed0

Modified Files
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doc/src/sgml/client-auth.sgml | 2 +-
src/backend/parser/scansup.c | 2 ++
src/bin/initdb/initdb.c | 7 +++----
3 files changed, 6 insertions(+), 5 deletions(-)