IQR unbound

When quickloading plot I kept running into the following issue:
```
The variable BATCH-STATISTICS::IQR is unbound.
[Condition of type UNBOUND-VARIABLE]
```
Ignoring it works fine (at least for me) but is this supposed to happen?
Also, I was able to make it go away by commenting out the following lines at the bottom of statistics/src/batch:
```
+;; (defalias iqr interquartile-range)
+;; (export 'iqr)
```
I'm not sure if this is really an issue, but I spent a full day trying to figure it out so I thought I would at least leave my solution here if nothing else. If this is not an issue, feel free to correct me. Thanks!

Reproduce the quickload failure in plot and inspect statistics/src/batch, especially the defalias and export lines mentioned in the report. Confirm why BATCH-STATISTICS::IQR is unbound and verify that quickloading completes without the warning while the IQR functionality remains available.

Written by the indexing model from the issue text.