Column mis-spelling hints vs case folding

A newbie error that we see *constantly* is misunderstanding identifier
case-folding rules.  ISTM that commit e529cd4ff missed a chance to help
with that.  You do get a hint for this:

regression=# create table t1 (foo int, "Bar" int);
CREATE TABLE
regression=# select bar from t1;
ERROR:  column "bar" does not exist
LINE 1: select bar from t1;              ^
HINT:  Perhaps you meant to reference the column "t1"."Bar".

but apparently it's just treating that as a vanilla one-mistyped-character
error, because there's no hint for this:

regression=# create table t2 (foo int, "BAR" int);
CREATE TABLE
regression=# select BAR from t2;
ERROR:  column "bar" does not exist
LINE 1: select BAR from t2;              ^

I think this hint might be a lot more useful if its comparison mechanism
were case-insensitive.
        regards, tom lane