- generation of "unique" bind parameters has been simplified to use the same

- generation of "unique" bind parameters has been simplified to use the same
"unique identifier" mechanisms as everything else.  This doesn't affect
user code, except any code that might have been hardcoded against the generated
names.  Generated bind params now have the form "<paramname>_<num>",
whereas before only the second bind of the same name would have this form.

- bindparam() objects themselves can be used as keys for execute(), i.e.
statement.execute({bind1:'foo', bind2:'bar'})