Very slow deletion of thumbnail cache

[cosmin]

This is not really a bug report, it's rather an efficiency report.

My thumbnail cache was about 650MB, not too small, not too large...
When I hit the "Remove all" button in the Options window, XnView froze for a few minutes, until the entire cache was cleared. I was expecting this operation to be near-instant. I suspect this happened because the deletion algorithm is suboptimal. (It should be a linear-time algorithm.)

Merci de votre attention.

--
Cosmin