An ALTER TABLE statement which added a column and added
a non-partial index on it failed with:
            
"ERROR 1089 (HY000): Incorrect sub part key; the used
key part isn't a string, the used length is longer than
the key part, or the storage engine doesn't support unique
sub keys"
            
In a check introduced to fix an earlier bug (no. 26794),
to allow for indices on spatial type columns, the
test expression was flawed (a logical OR was used instead
of a logical AND), which led to this regression.
            
The code in question does a sanity check on the key, and
the flawed code mistakenly classified any index created
in the way specified above as a partial index.  Since
many data types does not allow partial indices, the
statement would fail.