Compilation with `infer_schema!` panics when table has column named `ops`

Somewhere in the macro expansion, there is code that imports ops from within diesel. If a column in a database is named ops, this causes conflicts within the macro.

I think that putting a note somewhere that this could happen may be enough; however, prefixing the internal variables or module names to something like _table_ops or something similar would be a more permanent solution.