Kill PerformanceWarning

[mrks]

As discussed in the fortnightly, the PerformanceWarnings have no clear semantics. Who is warned about what? Right now, they look like glorified TODO comments. Remove them and replace them with either TODO comments or explicit prints (especially in the TPC-C binary).

[tjjordan]

As discussed in the fornightly, a good solution is not yet found.

The use of print-statements worsens the spam to the console, which in general opinion should be prohibited.
It could be an option for extremely performance-critical codepaths, but I think it could be better to make them inaccessible.

Other discussed options were the use of a logging infrastructure or mentioning the warnings in comments or in a separate file, but this is very easy to ignore.

For further discussion a separate meeting is planned.